Damping Off. 311 



January 30th a small portion of this tissue was farther teased out and 

 mounted in fresh water in a cell culture. January 31st farther 

 growth had appeared and new oogonia and antheridia were 

 developed. This continued for several days in the same culture. 

 On February 1st at 12.30 p. m. as shown in Fig. 1, the egg cell in 

 the oogonium has formed and the antheridium curved over on one 

 side is full size hut the fertilization tube has not yet formed nor 

 has the gonoplasm differentiated, the granular protoplasm being 

 arranged in a network of threads. At 3.15 p. m. of the same day, 

 as shown in Fig. 2, the fertilization tube is complete, the gono- 

 plasm has formed and is about to pass through the tube, while a 

 very thin wall is forming around the egg cell except at the recep- 

 tive spot. At 9 p. m., Fig. 3, the gonoplasm has passed through 

 and the wall of the oospore is complete. Fig. 4 represents an inter- 

 calary oogonium which was observed in the stage figured, at 

 12.30 p. m., Febmary 1st. Two antheridia are here in contact with 

 the oogonium, s. a. a stalk antheridium and 5. a. a branch, antheri- 

 dium. In both cases the fertilization tube is complete, and the 

 gonoplasm has separated preparatory to passing through. The 

 curving of the stalk antheridium has turned the main thread to one 

 side, the branch antheridium arising quite closely by the side of the 

 oogonium has curved inward to the wall of this organ. At 3.30 

 p. m.. Fig. 5, the gonoplasm has passed through the fertilization 

 tube from both antheridia and a thin wall has formed around the 

 now fertilized egg. Fig. 6 at 12 p. m., showed a terminal oogonium 

 with two antheridia, one a stalk antheridium and one a branch 

 antheridium, it being difficult in this case to say which is the stalk 

 and which is the branch. An accident happened to this specimen 

 ^nd it was not seen again. Fig. 7 represents two terminal oogonia 

 ■each with a stalk antheridum, first observed at 9 p. m,, Febru- 

 ary 1st. At this time in the case of oogonium a, the egg cell is 

 formed, and the gonoplasm in the antheridium has separated, 

 while in oogonium b, the egg cell has not yet formed. From the 

 fact that the stalk antheridium was on the undersideof oogonium 5, 

 when it was first observed, the stage of its development could not be 

 seen. At 2 p. m., on February 2d, however, fertilization was com- 

 pleted in both as shown in Fig. 8. Fig. 9 represents an oogonium 

 with a fertilized egg and two antheridia in contact with its wall; 

 one, a, a stalk antheridium whose gonoplasm took part in the act of 

 fertilization, and one, h, a branch antheridium from a different 



