242 BULLETIN 94. 



of the oospore is complete. Fig. 4 represents an intercalary 

 oogonium which was observed in the stage figured, at 12:30 p. M., 

 Feb. i. Two antheridia are here in contact with the oogonium 

 s. a. a stalk antheridium and b. a. a branch antheridium. 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 and it was not seen again. Fig. 7 represents two ter- 

 minal oogonia each with a stalk antheridium, first observed at 9 

 p. M., Feb. i. At this time in the case of oogonium a, the egg 

 cell is formed, and the gonoplasm in the antheridium has sepa- 

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

 the fact that the stalk antheridium was on the under side of 

 oogonium d, when it was first observed, the stage of its develop- 

 ment could not be seen. At 2 p. M., on Feb. 2, however, fertili- 

 zation was completed in both as shown in fig. 8. Fig. 9 repre- 

 sents an oogonium with a fertilized egg and two antheridia in con- 

 tact with its wall ; one, a, a stalk antheridium whose gonoplasm 

 took part in the act of fertilization, and one, b, a branch antheri- 

 dium from a different hypha from that on which the oogonium is 

 borne. From the latter the gonoplasm was not used. 



These oospores or fertilized eggs mark a very important phase 

 in the life history of the fungus. They will eventually germinate 

 and produce the mycelium again, which under favorable condi- 

 tions will start the disease anew. But the remarkable thing about 

 the oospores is that they cannot germinate immediately, except in 

 rare instances, but must undergo a long period of rest, and hence 

 are sometimes termed resting spores. In this condition they are 

 capable of resisting degrees of cold and dryness which would prove 

 fatal to the vegetative portion of the fungus. This accounts partly 



