NOTES AND MEMORANDA. 179 



amount of variation, so that it is sometimes difficult, before 

 the fertilisation, to distinguish between them (b). 



The process of fertilisation may be regarded as a conjuga- 

 tion, since the spore proceeds from the union of the whole 

 protoplasm of two individuals ; it is hence a zygospore, but 

 also, on account of the sexual differentiation of the parent 

 individuals, it may be designated as an oospore. 



The male individuals which conjugate may be of any age; 

 even such can be met with in the act of fertilisation which 

 have not advanced in their development beyond a germinat- 

 ing zoospore. 



Conjugation begins by the whole protoplasm of the female 

 plant passing out through a circular opening in the same 

 manner as described for the zoospores; hence the body of the 

 female plant behaves as regards the production of the oospore 

 as a " prosporangium." So soon as it has all emerged it 

 forms an oval mass, lying in front of the opening, and it cor- 

 responds nearly to a " gonosphere," as yet the author thinks 

 without membrane. Fertilisation takes place by the union 

 of the plasma of a female with the whole of that of a male- 

 plant. The gonosphere comes in contact with the stipes- 

 like haustorium of an adjoining male-plant; its membrane 

 becomes resorbed at the point of contact, whereupon the 

 whole plasma becomes emptied through the haustorium and 

 combines with that of the female — a process requiring several 

 hours to complete. 



The zygospore now becomes surrounded by a cell-mem- 

 brane, at first simple and delicate, afterwards double and 

 thicker — an intine and an exine, the latter becoming yellow, 

 but remaining smooth (b, o) ; the empty walls of both the 

 parent-cells become shut off, remaining, however, in con- 

 nection with the spore (b, o), usually diametrically opposite 

 one another. 



It is noteworthy that the stipes-like haustorium of the male 

 often developes lateral ramifications which manifestly, pre- 

 viously to conjugation, serve to absorption of nutriment, sub- 

 sequently thereto serve, on the other hand, to the emptying 

 of the male plasma. Sometimes minor haustoria are given 

 off from the periphery of the resting-spore. The mature 

 resting-spore is usually oval. 



Spinous Resting-Spores. — In the same culture and at the 

 same time that the smooth-walled oospores are produced in 

 the manner described there are formed also sexually-developed 

 resting-spores of yet another kind. These are almost con- 

 stantly globular, surrounded by a thick double membrane 

 with a yellow-coloured exine and f,ne spines (a). They do 



