Actinodiycetes
Actinodiycetes The Mycelial Organization Of This Group Allows The Streptomycetaceae To Develop Aerial Hyphae Bearing Dry, Powdery Spores—the First Example Of The Sporophore Elevation Device, Common In More Elaborate Organisms, For Raising The Spore-producing Organ Above The Substratum And Towards The Moving Layers Of The Atmosphere. Take-off Conditions In The ...
Aerobiology
Aerobiology Is A Synthesis: Just As The Geographer Draws Upon Astronomy And Geology, So The Acrobiologist Draws Upon Many Sources. To Under Stand The Environment Of The Air-spora We Must Go To Meteorology. A Fuller Account Of The Relevant Features Of The Atmosphere Than That Given Here Can Be Found ...
Air Masses
Air Masses The Fact That Air May Have The Same Temperature And Humidity Over A Wide Geographical Area Has Given Rise To The Concept Of The Discrete Air Mass, With Properties Different From Adjacent Air Masses And Separated From Them By `fronts'. When An Air Mass Remains Stationary For Some ...
Algae
Algae Adaptations Facilitating Take-off Into The Air Are Unknown In The Algae, Though Some Of The Simpler Types Of Algal Cells Get Into The Air Regularly. Pettersson (194o) Suggested That Clilamydomonas Nivalis Is Carried Away From Its Habitat On Snow-fields And Glaciers In Melt-water And Becomes Airborne By Splash In ...
Angiosperms
Angiosperms Details Of Flowering-plant Pollination Mechanisms Are Given By Mari Laun (1895), Knuth (1906), Erdtman (1943, 1957), Wodehouse (1945) And Others. (i) Grasses, Rushes, Sedges And Their Allies. The Gramineae, Cyperaceae, Typhaceae, And Juncaceae Are Typically Wind-pollinated. From The Raised Inflorescences Of Grasses, The Anthers Are Extruded On Long Filaments ...
Bacteria
Bacteria Moving Air Does Not Normally Detach Bacterial Cells From The Surface Of A Colony, At Least When This Is Slimy, And In The Absence Of An Active Discharge Mechanism Natural Processes Capable Of Producing An Aerosol Of Single Bacterial Cells Are Unknown. Mechanical Disturbance Of Dust, Clothing, Surgical Dressings, ...
Bryophytes
Bryophytes Spores Of Mosses And Liverworts Are Formed In Sporangia Which Are Typically Raised On Stalks Above The Substratum, But The Structure Of The Sporangium Is Quite Different In The Two Groups. The Moss Sporangium Is A Firm `box' Opening At The Top, Whereas The Liverwort Sporangium Breaks Open Completely, ...
Circulation Of The Atmosphere
Circulation Of The Atmosphere Under The Influence Of Pressure Differences Resulting From Solar Heating, And Of Friction Between Wind And The Rotating Earth, A General Pattern Of Atmospheric Circulation Is Set Up. The Surface Winds Shown In Atlases Are The Ground-level Part Of A Three-dimensional System That Has Not Yet ...
Comparison Of Theories Of
Comparison Of Theories Of W. Schmidt And Sutton According To Schmidt's Theory, = 2at/p, So, Because T — X/u, We Have Log A = I Log X -f 1 Log (2a/pu). If This Relation Holds True In Field Tests, Plotting Experimental Data For Log A Against Log X Should Give ...
Controversy On Spontaneous Generation
Controversy On Spontaneous Generation Leeuwenhoek Had Come To Doubt The Belief, Dating From Aristotle, That Flies, Mites, And Moulds Were Generated Spontaneously By Decaying Animal And Vegetable Matter. To Him It Seemed Likely That Animalcules Could Be Carried By The Air, And This Provided An Alternative Explanation To Spontaneous Generation. ...
Convective Layer
Convective Layer This Layer Extends From About I Km. Above The Ground To The Top Of The Troposphere At About Io Km. As In All The Layers Constituting The Tropos Phere, The Temperature Continues To Decrease With Height To The Top Of The Convective Layer, Though Diurnal Temperature Variation Is ...
Deposition Processes We
Deposition Processes We Have Now Considered Airborne Micro-organisms As Diffusing Clouds. Before We Can Discuss Processes By Which They Are Deposited In The Com Plex Outdoor Environment, We Must Deal With Deposition Processes Under Simplified, Ideal Conditions. The Word `deposition' Is Used In A General Sense To Include All Processes ...
Diffusion As A Result
Diffusion As A Result Of Atmospheric Turbulence Watching The Drift Of Smoke From A Bonfire Or Factory Will Convince The Observer That Wind, Instead Of Having A Steady Streaming Motion, Is Characteristically Turbulent As Described In Chapter Iii. According To Brunt (1934), Large Numbers Of Small-scale Eddies, Whose Periods Are ...
Dispersion Of The Spore Cloud
Dispersion Of The Spore-cloud It Is Still Convenient To Speak Of Clouds Of Spores—not, Indeed, Keeping Together In The Manner Of Locust Swarms, But Tending To Become Dispersed While Suspended Passively In The Atmosphere. Sampling A Region Small Enough In Relation To The Size Of The Cloud May Then Reveal ...
Early Microscopists And The
Early Microscopists And The Discovery Of Spores After Lucretius, More Than 1,500 Years Passed Before Men Even Began To Be Aware That The Air Teems With Microscopic Living Organisms. The Discovery Had To Wait Almost Until The Invention Of The Micro Scope. For A Long Time After Aristotle And Theophrastus, ...
Effects Of Sedimentation
Effects Of Sedimentation The Effects Of Spore Fall In Still Air Can Be Observed Indoors, Particu Larly If A Room Is Left Closed And Unoccupied—a Fact Noted Early In The Study Of Air Hygiene By Workers Using Hesse's Horizontal Tube Method Of Air Sampling, Or Some Modification Of It (see ...
Factors Determining Velocity Of
Factors Determining Velocity Of Fall One Effect Of Its Molecular Activity Is That The Air Is Viscous, I.e. It Resists The Movement Of Solid Particles. A Small Particle Liberated Into The Air From A Resting Position Tends To Fall With An Acceleration Due To Gravity; However, The Resistance Of The ...
Field Experiments On Diffusion
Field Experiments On Diffusion Of Spore-clouds Several Experiments Have Now Been Reported That Give Data From Which It Is Possible To Test The Applicability Of Eddy Diffusion Theories To Diffusion Of The Spore-cloud In A Horizontal Direction. Stepanov (1935) Used Artificial Sources Of Spores That Were Liberated At A Point ...
Fungi
Fungi Adaptations Facilitating Air Dispersal Show More Diversity In The Fungi Than In Any Other Group—except, Perhaps, Adaptations For Seed Dispersal Among The Flowering Plants. They Vary From The Passive But Quite Effective Processes In The Fungi Imperfecti, To The Spectacular Ballistic Feats Of The Ascus Gun. The Various Mechanisms ...
Gymnosperms
Gymnosperms Conifer Pollen, Instead Of Being Formed In Stalked Anthers As Is That Of Angiosperms,' Is Produced In Two Or More Pollen Sacs On The Lower Side Of The Male Cone-scales. The Pollen Grains Are Large And Often Bear Two Conspicuous Air-filled Bladders Which Decrease The Density Of The Particle ...
Horizontai Diffusion
Horizontai. Diffusion Values For C And In Calculated From Various Spore-dispersal Tests Are Shown In Table Viii. Evidently For Microbiological Work We Must Use High Values Of Perhaps Because We Are Concerned With Longer Sampling Periods Than Sutton. We Shall Therefore Choose C,, = O•8 (metre)t, And = (metre) , ...
Horizontal Diffusion We
Horizontal Diffusion We Have Now Described The Particles Composing The Air-spora And The Relevant Properties Of The Atmosphere. What Happens To The Particles After They Have Been Launched Into The Atmosphere ? Common-sense Tells Us That They Become Dispersed—in The Sense That Their Concentration Per Unit Volume Of Air Decreases ...
Impaction On A Rotating
Impaction On A Rotating Sticky Cylinder Rotating The Cylinder At A Peripheral Speed Comparable With The Wind Speed Would Be Expected To Reduce The Thickness Of The Boundary Layer On The Surface, To Induce The Well-known Magnus Effect, And To Produce A Local Rotation Of Air Round The Cylinder Itself. ...
Impaction On Cylinders
Impaction On Cylinders The Efficiency Of Impaction On Vertical Sticky Cylinders Is Increased By: (i) Increasing Wind-speed; (2) Increasing The Mass Of The Particle (by Increase In Size Or Density); And (3) Decreasing The Diameter Of The Cylinder (except That Large Particles, Such As Lycopodium Spores, Tend To Blow Off ...
Laminar Boundary Layer
Laminar Boundary Layer In Contact With The Surface Of The Earth And All Projecting Bodies Is A Microscopically Thin Layer Of Air Held Firmly By Molecular Forces. Except For Molecular Diffusion This Layer Is Still And Windless. Above This Windless Film The Atmosphere Is Usually In Motion, Set Going Either ...
Lichens
Lichens The Fungus Component Of Lichens Discharges Ascospores From Typical Apothecia Or Perithecia, Or Basidiospores From Basidia. Fragments Of The Thallus Including Both Fungal And Algal Components Are Blown About Freely. Rounded Groups Of Algal Cells Surrounded By Fungal Hyphae, Separating Off From The Lichen Thallus As Soredia, Are Also ...
Local Eddy Layer
Local Eddy Layer For Biological Purposes We Need To Add The `local Eddy Layer'. Even In Streamlined Air, Local Stationary Eddies May Exist Behind Small Rough Nesses; And, As Will Be Shown On Page 35, Air-flow Over A Cup-shaped Depression May Set Up A Rotation Pattern Sufficient To Throw Dust ...
Myxo Mycetes
Myxo Mycetes (mycetozoa, Myxogastrales) The Slime-moulds Are A Group Thoroughly Adapted To Wind Dispersal. Some, Such As Reticularia, Merely Expose A Dry, Powdery Spore-mass On A Cushion Raised Above The Substratum. Others, Such As Stemonitis And Trichia, Expose Small, Dry Spore-masses On Stalks At Most A Few Millimetres High. The ...
Night Radiation And Temperature
Night Radiation And Temperature Inversion At Night, Wind Speeds Tend To Diminish; The Laminar Boundary Layer Then Becomes Thicker Than By Day And The Turbulent Boundary Layer May Become Thinner, Being Reduced To Perhaps Only Io To 15 Metres In Thickness. These Changes May Be Carried Still Farther If The ...
Pollen Distribution At Different
Pollen Distribution At Different Altitudes Mean Diameters Of Birch Pollen On The Night Flight, A To (table Iii). The Size-range Recorded By Rempe Varied From Z3µ To 27-5 ?, So It Is Evident That Even At Night The Sorting Effect Was Not Great—a Difference In Altitude Of R,000 Metres Was ...
Pollination Of Phanerogams
Pollination Of Phanerogams Insects And Wind Are The Chief Agents Of Cross-pollination In Flowering Plants. Other Pollinating Agents That Are Effective In A Far Smaller Number Of Species Include Water And Humming-birds. There Are Probably Ten Times As Many Entomophilous (insect-pollinated) As Anemophilous (wind-pollinated) Species Of Flowering Plants In The ...
Problems Of Take Off
Problems Of 'take-off' As Described In Chapter Iii, The Surface Of The Ground Or Plant Is Covered By A Thin Layer Of Still Air And By The Laminar Boundary Layer Of Slowly Moving Air; A Spore Will Fall Through This Composite Zone Under The Influence Of Gravity. To Tap The ...
Pteridophytes
Pteridophytes Spores Of Pteridophytes (ferns And Their Allies) Are Formed On The Fronds Within A Closed Sporangium, From Which They Are Dispersed Into The Air By A `sling' Mechanism Depending On Water-rupture Under Great Tension As The Maturing Sporangial Wall Dries (see Ingold, 1939). Pettersson (1940), In Finland, Found That ...
Role Of Convection
Role Of Convection When The Surface Of The Ground Is Heated By Sunshine The Lowest Layer Of Air May Be Heated In Turn. If A Large Temperature Lapse-rate Is Established, The Atmosphere Becomes Unstable, Because The Less Dense Ground-layer Of Air Tends To Rise And Carry Its Load Of Microbes ...
Sedimentation In Still Air
Sedimentation In Still Air All The Particles With Which We Are Concerned Are Heavier Than Air. In Still Air They Sink With Characteristic And Constant `terminal Velocity'. Stillness As A Quality Of Air Is Only Relative. In The Laboratory We Can Make The Air As Still As Possible By Eliminating ...
Speculations On The Origin
Speculations On The Origin Of Disease Classical Writers Believed That The Wind Sometimes Brought Sickness To Man, Animals, And Crops. Hippocrates, The Father Of Medical Science, Held That Men Were Attacked By Epidemic Fevers When They Inhaled Air Infected `with Such Pollutions As Are Hostile To The Human Race'. A ...
Spore Liberation Up
Spore Liberation Up To Now We Have Considered Only The Physical Properties Of Spores And Of Their Environment. Spores, However, Are Parts Of Living Organisms Whose Evolution Has Been Extensively Moulded By The Environment. The Air Spora Comes Mainly From Species Which Are Highly Adapted Towards Using Wind Energy For ...
Take Off Mechanisms In Cryptogams
Take-off Mechanisms In Cryptogams Etc. Spore- And Pollen-liberation Mechanisms Have Formed The Subject Of Classical Researches In Biology For Over A Century. The Wealth Of Informa- . Tion In The Scattered Literature On Land Plants Is Reviewed By Ingold (199), And Knowledge About Bacteria By Wells (i955), But For Protozoa ...
The Allergists
The Allergists The Idea That Men, Other Animals, And Plants, Could Become Infected By Microbes Which Set Up Pathological Changes, Had Been Made Acceptable By The Analogy Of Sterile Organic Infusions That Become Infected With Putrefying Microbes. The Idea Became Widely Accepted During The Latter Half Of The Nineteenth Century ...
The Atmosphere And Its
The Atmosphere And Its Layers The Atmosphere Is Usually Recognized As Layered; Some Of Its Main Features Are Illustrated In Fig. 3, In Which Altitude Is Drawn On A Logarith Mic, Instead Of A Linear, Scale In Order To Allow The Various Layers To Be Represented Together On One Page ...
The Germ Theory Of
The Germ Theory Of Disease We Must Now Look Back And Trace The Growth Of The Microbial Theory Of Disease, That Had Been Developing For More Than A Century. The Minute Growths Of Fungus Noticed For Centuries On Mildewed Or `rusted' Plants Were Believed To Be A Consequence Of The ...
The Hygienists And Their
The Hygienists And Their Investigation Of The Air While The Causes Of Infectious Diseases Of Man And Animals Were Being Unravelled In Laboratories And Clinics, A Series Of Field Investigations Into The Air-spora Was In Progress To Find Whether Fluctuations In Number And Types Of Microbes Present In The Atmosphere ...
The Microbiology Of The
The Microbiology Of The Atmosphere. The Air We Breathe, Like Our Food And Drink, Varies In Quality From Time To Time And From Place To Place. This Fact Was Recognized Many Centuries Before Industrialized Man Assumed The Right To Pollute The Atmosphere With Poisonous Chemicals And Radioactive Isotopes. In Britain ...
The Stratosphere
The Stratosphere In This Region, Which Extends Upwards From The Tropopause To The Limit Of The Atmosphere, The Temperature Lapse-rate, Characteristic Of The Troposphere, Is Zero Or May Even Be Reversed. The Height Of The Tropo Pause Varies With Season, Latitude, And Other Factors. The Bottom Of The Stratosphere May ...
The Troposphere
The Troposphere The Troposphere Is The Name Given Collectively To The Lower Layers Of The Atmosphere Extending From The Ground To A Height Of Approximately Io Km., And Is A Region Characterized By A Decrease In Temperature With Increasing Height—the Temperature Lapse. Air Is Relatively Transparent To The Short-wave Radiation ...
Transitional Or Outer Frictional
Transitional Or Outer Frictional Turbulence Layer Here Frictional Turbulence, Generated In The Layer Below, Still Domin Ates Vertical Diffusion, But It Dies Out Gradually Until, At The Top Of The Layer, Both Turbulence And Diurnal Temperature Changes Disappear. Both Layers May Be Dusty, And The Top Of The Transitional Zone ...
Turbulent Boundary Layer
Turbulent Boundary Layer In This Layer, Where Flux Of Momentum Decreases Linearly With Height, Solid Obstacles, Arising At The Surface In The Laminar Boundary Layer, Project Into The Wind And Cause Eddies Which Break Away From The Surface And Travel Downwind. A Surface Is Aerodynamically Smooth In Conditions When The ...
Viruses
Viruses The Viruses Are Little Adapted To Independent Air Dispersal. Some Viruses Infecting The Animal Respiratory Tract Are Forced Into The Air On Droplets During Coughing And Sneezing; But Most Bacterial And Plant Viruses, If They Occur In The Air At All, Only Get There On `rafts' Of Debris Or ...
Wind Tunnel Study Of Impaction
Wind-tunnel Study Of Impaction The Following Account Is Based On Work With A Small, Low-speed Wind Tunnel Built At Rothamsted Experimental Station In 1949 (gregory, 1951; Gregory & Stedman, 1953) And Includes Some Hitherto Unpublished Data. The Wind-tunnel Consists Of A Horizontal Square Duct (fig. 11). The Two Ends Of ...