ASCOMYCETES. The Ascomycetes (sac-fungi) present structures and life histories that are very difficult to correlate with those of the Phycomy cetes. Some of the lower forms are undoubted ly sexual. There is present a female cell (ascogo nium or archicarp) fertilized by a discharge from a neighboring male cell (antheridium), the con dition recalling at once that in the downy mil dews. The fertilized female cell, however, devel ops a special system of filaments that finally pro duce the characteristic spore-containing sacs (asci). These filaments are generally associated with sterile portions of the original body to form a fructification called the ascocarp. The asco carp may be compared to a similar growth (cystocarp) produced from the fertilized egg of the red algx (Rhodophycere). The subject be comes further complicated, however, by an ap parent tendency among the Ascomycetes to give up sexuality. In some higher groups rep zed investigations have failed to demonstrate sexual organs, and the ascocarp in consequence probably develops without a sexual act. There have been attempts to homologize the ascus (spore-sac) with the sporangium (spore-ease) of the black molds, assuming that the large and variable number of spores in the latter structure became reduced and fixed to eight, the usual number in the former. Later studies upon the development
of the spores, however, indicate that the two structures are not related. It is then possible that the ascus is a special form of spore-case pe culiar to the Ascomycetes. There are a number of peculiar forms of spores in the Ascomycetes, developed at various periods in the life history, manifestly for purposes of distribution. They have been named conidia, pycnidia (qq.v.). etc. There are a great many fungi known only through some fructification of this character. For con venience they are placed in a group called the Ilyphomycetes or Fungi Imperfect'. Most of the Ilyphomycetes are believed to be imperfect forms of Ascomyeetes, but among them there are also large numbers of species that undoubtedly be long to other groups. There are practical rea sons for this artificial group, as many of the spe cies are economically important. Studies in their life histories are constantly bringing to light phases which determine their place among the natural groups, so that species are constantly being removed from this artificial assemblage.