142 



DIVISION II. COURSE OF DEVELOPMENT OF FUNGI. 



are several oospheres present the tubes often grow from one to another, and even 

 form branches which grow up to and past different oospheres, and sometimes even 

 pierce through the wall of the oogonium and pass outside it ; but they always remain 



closed and die in the course of 1-2 days 

 while the oospheres are . maturing. The 

 short tubes of Aphanomyces scaber are the 

 only ones which I have examined which 

 never showed this luxuriance of growth ; 

 they apply their apex firmly to the oosphere 

 which in this species is solitary, and re- 

 main in that position without change till 

 the oospheres ripen in 2-3 days' time. 

 These facts show that the antheridia and 

 fertilisation - tubes of the Saprolegnieae 

 must be considered to be homologous with 

 those of Pythium and that they may be 

 called by the same name : but there is no 

 ground for regarding them as really fer- 

 tilising organs ; for while in some species, 

 as Achlya polyandra and Saprolegnia 

 monoica, their mode of formation is always 

 such as has just been described, there are 

 other species in which the same plant may 

 have these antheridia with their fertilisa- 

 tion-tubes and at the same time antheridia 

 without tubes, or oogonia without any an- 

 theridia (Aphanomyces scaber, Saprolegnia 

 hypogyna) ; and lastly there are species 

 or races, extremely like those named above 

 in other respects, which very seldom or never 

 form antheridia. In all these cases the 

 formation of oospheres and oospores does 

 not vary in the smallest detail. 



The ripe oospores remain dormant dur- 

 ing a time which varies from some days 

 to some months according to the species, 

 and germinate in the same forms as in 

 the Peronosporeae (Fig. 69 D, E}. All 

 the different forms of germination de- 

 scribed in the Peronosporeae have also 

 been observed in most of the species of 

 Saprolegnieae which have been examined, 

 the form varying according to the ex- 

 ternal conditions, especially those of nutrition; but in some species certainly only 

 one or the other form of germination has been observed. In a new species, Aplanes 

 Braunii, the- whole course of the development, as far as my observations go, is usually 



FIG. 69. A C. Achlya racemosa, Hildebr. A end of a 

 fertile branch with an empty sporangium at J surmounted by 

 a head of gonidia out of which most of the spores have already 

 swarmed away. Beneath it on short lateral branches are 

 three oogonia with anthcricli.il branchlets ; a before the deli- 

 mitation of the oogonium and antheridia ; b and c in the same 

 stage as B ; both oogonia have two antheridia, and * has six, 

 t seven oospheres. B oogonium with two oospheres and an 

 antheridium resting on it ; a fertilisation-tube from the an- 

 theridium has reached the surface of the nearest oosphere. 

 C a ripe oospore. D K. Achlya polyandra. Dan oogonium 

 with three germinating oospores about five weeks after 

 maturity. The short germ-tubes of two of the oospores are 

 protruding from the oogonium, the third lies bent inside it. 

 The oogonium contains also two oospores which have not 

 yet germinated, one of which is shown in the figure. E a 

 germinating oospore which has formed a small sporangium 

 with a head of spores. A magn. 145, B and C 375. D and 

 E 225 times. 



