ORDER LABOULBENIALES 213 



ture may become more complex by the longitudinal division of the cells 

 to form a body several cells in thickness from whose sides the appendages 

 and the male and female organs may arise. In Zodiomyces vorticellarius 

 Thaxter the main plant body is multicellular and widened at the top, 

 bearing on the flattened upper surface many filamentous appendages and 

 the sexual organs. Some of the larger forms lie prostrate on the body of 

 the host, rooting at various points by means of rhizoids. (Fig. 71.) 



In most of the genera of the order the antherids are flask-shaped 

 organs. The apex opens and a uninucleate sperm is pushed up into the 

 neck by the division of the nucleus and cytoplasm of the body of the 

 antherid. By successive formation of sperms in this way those previously 

 formed are pushed out of the neck. They are apparently naked cells, en- 

 tirely devoid of cilia or flagella. Sometimes several flask-shaped antherids 

 open into a common cavity with a single opening to the outside. In a 

 few genera the sperms are exogenous, being produced by the abstriction 

 of a terminal cell of a short, slender branch from an appendage. Such 

 sperms appear to possess a very thin cell wall. (Fig. 7 IE, H.) 



The female reproductive branch ("archicarp" of some authors) usu- 

 ally consists of a row of three cells, from the base to the apex respectively 

 the oogone ("carpogenic cell"), trichophore, and trichogyne. The first 

 two are nearly or completely surrounded by, usually, a single layer of 

 closely adhering protective cells. The trichogyne is usually one-celled 

 but may divide into several cells and is simple or extensively branched. 

 Perhaps in most cases the sperms are brought into contact with the 

 trichogyne by the active movements of the insect host as it brushes 

 against surrounding objects or other insects. Possibly in the case of 

 aquatic insects, or those frequenting wet places, water currents may bring 

 about the transfer of sperms to the trichogyne. In the genus Zodiomyces 

 the elongated trichogyne seeks out and unites with the sperm. In some 

 species antherids are unknown and the development of the oogone is 

 probably apogamous, (Fig. 71A-C.) 



After fertilization the oogone divides into about three cells, the bi- 

 nucleate middle cell of which now buds out laterally on all sides to form 

 numerous binucleate asci in which the two nuclei fuse and then divide 

 in the usual way to form eight nuclei. All eight or only four of these 

 nuclei serve as the centers of origin of the ascospores, in the latter case 

 the other four nuclei undergoing degeneration. The ascospores usually 

 are elongated and become two-celled. The ascus walls digest and leave 

 the numerous ascospores in a probably somewhat sticky gum in the cavity 

 of the considerably enlarged spore fruit whose walls have increased in 

 thickness. Eventually the ascospores are discharged between the apical 

 cells and because of their sticky walls adhere to objects with which they 

 come in contact, such as the body of another insect. In the latter case 



