Observations on SaprolegniecB. 139 



proach was in the unopened antheridium, where a small papil- 

 lary projection extended into the female organ; moreover, 

 where the antheridium had already been emptied of its "fecun- 

 dating corpuscles," its walls were very intimately connected 

 with the inner walls of the oogonium (Fig. 10). This inner 

 tube is figured and described by writers as being always pres- 

 ent, but my observations show that in this form it is rarely 

 produced; moreover, since the membrane of the oogonium is 

 not pierced by holes, * to allow the escape of spermatozoa, 

 which might take place through the delicate inner membrane, 

 I see no reason why fertilization is not as sure as when the 

 tube is present. This structure was noticed, not only with the 

 plants growing on one twig, but was true for different plants 

 found at different times. 



Soon after the gonospheres have thus been fertilized, each 

 is surrounded by a distinct membrane (PI. VI., Fig. 9), and 

 their contents undergo further change by dividing up into a 

 great number of bodies of equal size — the oospores or final pro- 

 duct of sexual generation. They are the resting spores, de- 

 signed at some indefinite time to give rise to parthenogenetic 

 forms. When undisturbed they remain in the oogoniurh a 

 long time, and escape by no regular dehiscence as is the case 

 in asexual generation, but the wall bursts irregularly, as also 

 the wall of the gonosphere, setting the spores free at no 

 definite time. I have seen gonospheres emptied, but have never 

 observed the spores in the act of passing out. In one instance 

 the oospores germinated in five days after their formation, 

 but as a rule, they remained at rest a much longer period. 



When germination takes place, the oospore swells to two 

 or three times its original size, with a dark center; the fila- 

 ment then produced, which is clear except at the base and 

 growing tip, is at first nearly the size of the spore (Fig. 13), 

 and not a mere protuberance from one side as in the germinat- 

 ing zoospores. They were not grown to the production of 

 fruit, and so I cannot say whether they ever reproduce them- 

 selves, as is sometimes the case in the genus Monoblepharis, 

 or whether they always give birth to sporangia-bearing 

 forms. 



* In the dioecious species of Achlya, the greater part of the species of Saprolegnia and some 

 of Mottoblepharis, the wall of the oogonium is pierced by many holes, which are undoubtedly 

 designed for the aid of fertilization (See PI. VII., Fig. 21, and description of Alonoblepharis 

 further on). 



