56 COMPARATIVE MORPHOLOGY OF FUNGI 



abjointed from the sporiferous hypha. This process may be repeated 

 as many as eight times, producing a chain of oogonia, each one of which 

 bears a small antheridium. Sometimes the latter are not formed. In 

 the hypogynous forms, the life cycle is essentially the same, except that 

 the positions of antheridium and oogonium are reversed. In the 

 antheridia as many as 32 sperms, corresponding to the nuclear number, 

 are formed. They resemble zoospores but are only half as large. They 

 swarm through an opening at the tip (Fig. 34, b and c). 



The processes which occur during the development and ripening of 

 the oogonium are not well known. The oogonia are always uninucleate; 

 their protoplasm forms an oosphere. Occasionally they mature later 

 than the antheridia, e.g., M. brachyandra is protandrous; consequently 

 self-fertilization is rare, although this species is not self-sterile. The 

 tip of the mature oogonium, which in some species is drawn out into a 

 papilla, gelifies. In M. insignis it opens intermittently, permitting 

 part of the substance to escape. The sperms flock together, probably 

 by chemotropism, and by amoeboid motion creep down the neck (Fig. 

 34, c). One of them fuses with the oosphere (plasmogamy). The 

 zeugite then remains at rest. In some exogynous species as M. brachy- 

 andra and M . sphaerica it moves, with revolution and amoeboid alterations 

 of form, to the bottom of the oogonium, and thence again toward the 

 tip whence it escapes (Fig. 34, d and e). Possibly this motility was 

 caused by the male flagellum being thrown off rather late. Near the 

 opening, it goes through a few amoeboid motions, becomes spherical, 

 surrounds itself with a membrane which gradually thickens and becomes 

 verrucose. In M. macrandra it leaves the oogonium entirely by its 

 own motion and matures elsewhere. In the endogenous species, e.g., 

 M. insignis, the oosphere remains in the oogonium and is there changed 

 to a hypnospore. Caryogamy takes place comparatively late after the 

 oosphere has left the oogonium, during the formation of the warts. After 

 a rest of several months, germination with meiosis (?) occurs through a 

 germ tube which perhaps develops to a zoosporangium. If the oosphere 

 is not fertilized, it is surrounded in the oogonium by a membrane and 

 develops parthenogenetically to a hypnospore. Conversely sperm 

 fertilization admits the possibility of cross fertilization; thus Woronin 

 considers M. macrandra, var. longicollis, a hybrid between M. poly- 

 morpha and M . spherica. 



Two other genera which have been important in the discussion of the 

 significance of the flagella for classification, Diblepharis with biflagellate 

 zoospores, and Myrioblepharis with multiflagellate zoospores, should be 

 considered in this family. In fitting the facts to the classification, 

 Woronin (1904) suggests the possibility that the biflagellate zoospores 

 belong to a parasite which has penetrated; in the second, Minden (1915) 

 suggests a mixture of Pythium and protozoa. 



