LEPTOMITALES 857 



the oogonium. In the Leptomitaceae the contents of the oogonium are 

 not differentiated into periplasm and ooplasm, as in the more highly 

 evolved Rhipidiaceae. 



The type of sexual reproduction found among members of the Lep- 

 tomitaceae appears less highly specialized than that among the Rhipid- 

 iaceae. In Apodachlya brachynema (Coker, 1923 ; Sparrow, 1932b; Indoh, 

 1953), which is characterized by the production of numerous lateral 

 moniliform branches, the oogonium arises as a terminal outgrowth of 

 the most distal segment of the branch. This continues to increase in size 

 by the flow of materials to it from the proximal segments. At maturity 

 it is a large globular structure filled with dense homogeneous mottled 

 protoplasm and subtended by the hypogynous cell from which it had its 

 origin. Like the oogonium, the smaller subterminal cell contains densely 

 granular protoplasm. A light spot (probably a pore) now appears in the 

 base of the oogonium and the contents of the hypogynous antheridial 

 cell slowly pass into the female gametangium. After a short rest period 

 this bright spot disappears and the contents of the fertilized egg become 

 organized into an oospore of typically saprolegniaceous character. The 

 wall thickens and one or more oil globules are formed. The oospore, 

 together with its attendant antheridial cell, may frequently be abscissed 

 from the remainder of the thallus. The mature resting structure, the 

 wall of which is distinctly thickened, nearly or, more often, completely 

 fills the oogonium (Fig. 69 C, p. 875). Kanouse (1927: 338) described 

 the oospore wall of A. brachynema as consisting of three parts, an outer 

 and an inner thin layer, and a middle thick one. In A. punctata the wall 

 is punctate as in the resting spore of the Blastocladiales (Minden, 1912 

 [1915]; Sparrow, 1933c) (Fig. 69 G-H). A more specialized antheridium 

 is formed in A. minima (Coker and Leitner, 1938). Here the hypogynous 

 cell gives rise to a branch, the tip of which is applied to the oogonium 

 (Fig. 69 D). The cell and the branch continuous with it function as an 

 antheridium. No fertilization tube is formed. Germination of the 

 oospore of A. brachynema by several multinucleate germ tubes has 

 been mentioned by Kevorkian (1935), but no details were given. Coker 

 and Leitner {he. cit.), who followed the process as it occurs in A. 

 minima, describe it essentially as follows: At the inception of germi- 

 nation the contents of the oospore gradually become granular throughout, 



