THE SPERMATOPHYTES. The earliest definite remains of plants of this sub-kingdom thus far recorded in America helong to the Devonian period. but in Europe they probably date as far back as the Upper Silurian. They developed slowly until Mesozoic time, when, as gyinno spurn's, they became 111e dominant type of vege tation, and from then onward, as angiosperms, they continued their upward development to the present time.
The gymnosperms were the earliest represen tatives, of which the extinct genera C'ordaites. Gingkophyllum. etc., may he considered as Origi nal types. As a class they were of relatively little importance numerically until the close of the Carboniferous period. when both cycads and conifers began to develop rapidly. and in early Mesozoic time these plants formed together more than 60 per cent. of the entire flora. This was the period of maximum development of the cycads in particular, after which they declined, and are now a rare and unimportant element in the living flora. The conifers apparently origi nated before the eyeads; their development was more uniform and they continued to be impor tant factors in the vegetation of both Mesozoic and Cenozoic time, as they are yet in the living flora. Genera such as Ilaiera. Aratwa rites. etc., closely allied to our Ginkgo and Norfolk Island pine. were in existence in the Jurassic and early Cretaceous periods. and these were followed by undoubted living genera, such as Sequoia, to which the giant trees of California belong; Firms, which includes our common pines, etc. As a whole, the conifers have continued to de cline in relative importance ever since the early part of the Cretaceous period.
The angiosperms may have had their origin in the Carboniferous period, but the few supposed Paleozoic forms described are very doubtful. Toward the close of the Jurassic period this class of plants was abundantly represented. and in the Cretaceous it rapidly developed into the dominant type. which position it has maintained ever since. In regard to the monocotyledons we know but little. The time of their first appear ance is not definitely established, and it was not until the palms made their appearance in the Cretaceous that they assumed any promi nence. Grasses and sedges probably preceded the palms, but their remains have mostly been found in rocks of Tertiary age. during which period the class. as a whole. may have con tributed about 10 per cent. of the entire flora.
It is probably in connection with the dieotyle dons that the greatest interest centres. Their origin is traced to certain archaic forms in the Jurassic and Lower Cretaceous deposits of North America and Europe. to which Saporta has given the name of proangiosperms. Some of these from the Potomac formation of Virginia suggest, superficially. a blending of the monocotyledons and dicotyledons, as seen in the genera Acacbc phyllum and Protecephyllum. Others, like Pro
torrhipis, Braseniopsis, etc., have certain char acters suggestive of relationship to those few dieotyledons which, in common with the mono cotyledons. possess an endogenous structure. and of which Nymphfea, Nelumbo. etc., are examples. Apparently the dicotyledons attained their high degree of development, both biologically and nu merically, more rapidly than did any one of the types of vegetation which preceded them. In the Middle Cretaceous they had become the dominant type, and they have continued so to the present time. Among the earliest identifiable genera are many whose relationship with living genera is more or less clearly defined, as indi cated in the names Pupulophyllum, Quereophyl Saliciphyllum, etc., while these were fol lowed by others like Sassafras, Platanus, Lirio dendron, Magnolia, etc.. \Odell it has been found impossible to separate generically from those now in existence. Living species have been recog nized as far back as the Lorene and the Tertiary, and in the Quaternary period it is probable that all were identical.
BIBLIth,RAPHY. The following may be cited as general eompends, text-hooks, and works of popular interest on the subject. Dawson, The Geological History of !'lasts (New York, 1888) ; Knowlton, "Fossil Plants as an Aid to Geology," in •Journal of Geology, vol. ii. (Chicago, 1894) ; Potonie, Lehrbuch der Pflanzenpahiontologic (Berlin, 1899) ; Saporta, Le monde des plontes avant Papparition dc Phonune (Paris, 1879) ; Saporta and Marion, Origind paleontologique des arbrcs, etc. (ib., 1888) ; Schenk, Die fossilea Pflanzenrcste (Breslau, 1888) ; Schimper, Traite de paleontologic regetale (Paris, 1869-74) ; Schimper and Schenk, Paleophytologie, being part ii. of Zittel's Handbuch der Paliiontologie (Munich and Leipzig, 1890) ; French trans lations of same by Barrios (Paris, Munich, and Leipzig, 1891) ; Scott, Studies in Fossil Botany (London, 1900) ; Seward, Fossil Plants as Tests of Climate (ib., 1892) ; Seward, Fossil Plants for Students of Botany and Geology (Cambridge, Eng., 1898) Von Solms-Laubach, Einleitung in die PaLaophylologie. etc. (Leip zig, 1887) ; Von Sohns-Lauhach, Garnsey, and Balfour, Fossil Botany. Being an Introduction to Pahrophytology from the Standpoint of the Bot unist (Oxford, 1891) ; Unger, Synopsis Plan tarum Fossilium (Leipzig, 1845) ; Unger, Genera et Species Plantarum Fossilinm (Vienna. 1850) ; Ward, "Sketch of Paleohotany," in annual Re port of the United Stales Geological Surrey, vol. v. (Washington. 1885) ; Ward, "Principles and Methods of Geologic Correlation by Means of Fossil Plants," in American Geologist, vol. ix. (Minneapolis, 1892) ; Ward, "The Geographical Distribution of Fossil Plants," in Annual Report of the United States Geological Surrey, vol. viii. (Washington. 1889) : Zeiller, Elements de paleo botanique (Paris, 1900).