%ofi THALLOPHYTES. 



But on the other hand the formation of oospores exhibits a certain resemblance 

 to the process of conjugation. It is distinguished from that of the Pandorineae in 

 this point of importance only, that the two coalescing sexual cells are not alike, 

 so that the fertilisation of Vaucheria and (Edogonium may be considered as a 

 higher form of conjugation from a morphological point of view. But the mode 

 of formation of many oospores displays also a greater or less resemblance to the 

 mode of fertilisation which we shall describe as a third type ; and in this respect 

 the Saprolegniese in particular present a similarity to certain Ascomycetes. 



3. Formaiion of Carpospores in Carpogonia. This type resembles the second 

 in the fact that the two sexual organs contribute in very different degrees to the 

 production of the fertilised body, the male organ only inciting to change, while 

 the whole of the further development of the plant proceeds from the female organ, 

 the result being the production of the Sporocarp. 



The female organ, which may consist either of one cell or of more, may be 

 designated by the general term Carpogomum. The male organs vary greatly 

 according to the group to which the plant belongs; they may be swarming or 

 passively motile antherozoids, or tubular PoUinodia ; and fertilisation may be 

 effected by the entrance of 'the antherozoids, as in the case of oospores, or by a 

 kind of conjugation, the sexual cells coalescing by means of openings in the cell- 

 walls of both, or finally by simple apposition and probably diffusion of a fertilising 

 substance. The product of fertilisation is sometimes a single cell germinating 

 directly or through the medium of zoospores ; but more generally a multicellular 

 body results, from which spores are finally produced. An alternation of generations 

 may here also be recognised, rudimentary or more fully developed according as the 

 structure of the fructification is simpler or more complicated. In the simplest 

 cases the sporocarp appears only as an appendage of inconsiderable size to the 

 plant; in the other extreme the fructification is able to continue an independent 

 growth for a considerable time, and thus constitutes a second alternating genera- 

 tion. These phenomena will be described more in detail in the special description 

 of the Carposporese. One essential difference between sporocarps and oospores 

 consists in this, that in the production of the former certain cells also take part 

 which were not immediately concerned in the act of impregnation; and that, with 

 the exception of the simplest cases, the portion of the fructification which produces 

 the spores is surrounded by a sterile envelope which serves merely for protection 

 or also for further nourishment. Fig. 164 illustrates some of the most different 

 forms of sporocarps. 



In ColeochcBte {A) the female organ or carpogonium (hitherto described as the 

 oogonium) consists of a single cell w which runs out upwards into a long narrow 

 canal opening at the apex. Fertilisation is effected by small roundish swarming 

 antherozoids m, and as a consequence the portion of the protoplasm (oosphere) 

 which occupies the basal part of the cell becomes invested with a firm cell-wall. So 

 far the phenomena are the same as in the formation of the oospores of Vaucheria 

 or (Edogonium^ the only important difference consisting in the long canal formed by 

 the cell-wall. A more essential deviation is now manifested in that the body which 

 previously had the appearance of an oospore grows considerably after fertilisation, 

 and in the fact that the effect of fertilisation shows itself also in the growth of the 



