OOMYCETES 



55 



tions, M. brachyandra forms moniliform gemmae with thick, brownish 

 walls. Reproduction takes place by zoospores and oogonia with antheri- 

 dia (Thaxter, 1895; Lagerheim, 1899; Woronin, 1904; Laibach, 1926). 



The zoospores develop as follows: In the upper, often somewhat 

 thickened part of a hypha, protoplasm with numerous nuclei collects, 

 and is abjointed from the vacuolate portion. By its cleavage, there are 

 formed one or two series of uninucleate zoospore initials which become 

 zoospores in an unknown manner and swarm through an opening at the 

 tip of the sporangium (Fig. 34, a). After some time they come to rest, 

 surround themselves with a membrane and germinate. Subsequently 

 many lateral sporangia may grow out behind each other, so that generally 



Fig. 34. — Monoblepharis macrandra. a, Zoosporangium ; M. sphaerica. b to e, 

 Fertilization; Og, oogonia; An, antheridia producing sperms; S, oospores. (After Woronin, 

 1904.) 



only a portion of the hyphae participates in sporangial formation; thus 

 sporangial conditions result which give the impression of sympodial 

 branching. In other cases proliferation occurs, i.e., a new sporangium 

 arises beneath an old one and grows through its empty membrane. 



The antheridia are epigynous in Monoblepharis insignis, and M. 

 brachyandra, hypogynous in M. spherica and M. macrandra (Fig. 34, 6). 

 In the first, the antheridium, like a zoosporangium, is cut off as a terminal 

 cell. The hypha below the septum forms a lateral outgrowth, the neck 

 of the oogonium, and the oogonium itself is abjointed from the rest of 

 the hypha. Thus the antheridium is borne on the oogonium. A new 

 lateral outgrowth develops beneath the oogonium; its tip is separated 

 as an antheridium while the remainder swells to an oogonium and is 



