1776 



Journal of Applied Microscopy 



The time of spermatozoid formation varies somewhat in different localities 

 and also in different seasons. As mentioned before, in Tokyo, Mr. Hirase found 

 the spermatozoids for the first time on September 9th, 1896. In 1897 sperma- 

 tozoids were seen by Mr. Fujii on the 12th, and by Mr. Hattori on the 13th of 

 September. In the following year spermatozoids were first observed by Mr. 

 Shibata on September 16th ; but as about half of the ovules then examined had 



no indication of a pollen- 

 tube, — the pollen-tube hav- 

 ing been ruptured by dis- 

 charging the spermatozoids 

 — the formation of the latter 

 must have commenced earlier 

 than the above date. We 

 were able to find the largest 

 number of spermatozoids on 

 the 17th and 18th of Septem- 

 ber, and even as late as the 

 '22d a few were observed. In 

 1899 I observed several sper- 

 matozoids on September 7th. 

 From the above men- 

 tioned facts, we may see that 

 in Tokyo spermatozoids of 

 Ginkgo are developed be- 

 tween the 7th and 22d of 

 September. This would take 

 place later in a colder climate 

 and earlier in warmer locali- 

 ties. Assuming that this 

 would be the case, Mr. Fujii, 

 after no more spermatozoids 

 were to be found in Tokyo 

 in September, 1898, made a trip to Sendai, about two hundred miles northeast 

 of Tokyo, to make further observations, and as he had expected, sperma- 

 tozoids were still developing there, the largest number being observed on 

 the 27th. Mr. Bessey mentions that in Washington the spermatozoids are 

 developed between August 25th and September 10th, as extremes, the most 

 favorable time for finding them being September 1st to 3cl. It is also prob- 

 able that this date may differ in different trees in the same locality ; but two trees, 

 different in size, in the botanical garden, were found to develop the sperma- 

 tozoids almost simultaneously. 



In the mature ovule of Ginkgo, unlike that of the conifers, the nucellus is 

 reduced to a thin paper-like layer which forms a cap over the endosperm. The 

 pollen-tube is attached to the nucellus by the finely branched, root-like tip (Fig. 

 5), and the whole oval or oblong tube hangs down in the space between the 



Fig. 2. — A. Mature pollen grain, showing the persisting 

 vegetative cell {v), the central cell (<-), the tube cell (/) 

 and a remnant of the disorganized first vegetative cell 

 (t''); B. Development of pollen-tube, showing the 

 nuclei of, vegetative cell [v. //.), stalk cell (j-. «.), and 

 generative cell (;,'■. ;/.), and a part of pollen-tube; C. 

 A later stage, the generative cell ( g. c.) becoming 

 larger, with minute blepharoplasts (/') just appeared; 

 D. The generative cell still more enlarged, radiations 

 having appeared around the blepharoplasts ; x .jOO. — 

 After Hirase. 



