582 Scientific Proceedings, Boyal Dublin Society. 



transfers from cultures rich in oogonia become themselves, in due time, 

 also well provided with them. 



It was found that oogonia developed sooner, more abundantly, and with 

 greater regularity on Quaker-Oat agar than on Clinton's oat-juice agar. 

 Thus six out of the nine series produced oogonia on Clinton's medium, only 

 one of them abundantly, and the other five somewhat spasmodically ; but 

 when the nine were transferred to the Q,uaker-Oat medium, oogonia soon 

 began to be produced in all of them, and in most of them quite plentifully. 



As regards the time taken for oogonia to make their first appearance, it 

 would appear that continued culture on the oat-medium, with several 

 transfers to fresh tubes, is desirable before these bodies develop, at least in 

 any quantity. 



In the case of the series M. 7, oogonia were first found, and in abundance, 

 about one month from the start of the pure culture, and in the second 

 transfer. In tlie case of series C. 1, about ten days later. In the ease of 

 the other members of the nine series, a few showed some oogonia, and the 

 others none over a period of about sis months, during which they were being 

 grown, with transfers at suitable intervals, on Clinton's Oat agar. Oogonia 

 first began to appear in relative abundance and with constancy when the 

 transfers were made on to our own Quaker-Oat medium at the end of 

 February, 1912. 



When a small piece of a culture in which oogonia have already developed 

 is transferred to a fresh tube, the time taken for oogonia to develop in the new 

 culture varies considerably. The shortest time observed by us has been six 

 days, but it is frequently very much longer than this. 



On two occasions sets of parallel cultures were made with a view of 

 ascertaining whetlier the oogonia would develop better in total darkness than 

 under the alternating conditions of diffused daylight and the darkness. of 

 night. The results showed in both cases that the oogonia developed more 

 rapidly and more abundantly in total darkness. 



(2) Development of Oogonia and Ooqjores in the absence of Antheridia, i.e., 

 jmrthenogenetically. — The oogonia arise, as a rule, as terminal swellings on 

 fairly stout lateral liyphae ; but they may also arise laterally oa a hypha. 

 (See fig. 7, Plate XLVI.) The contents consist at first of finely granular 

 protoplasm, without oil-drops, similar to that found in the general mycelium. 



As the terminal portion of the hypha proceeds to swell, its contents become 

 more dense (see fig. 4, Plate XLYI) ; eventually oil-drops appear ; and its 

 wall, which becomes the wall of the oogonium, becomes brown in colour, thus 

 hiding from view to a great extent the subsequent changes undergone by the 

 contents. 



