42 MORPHOLOGY OP SPBRMATOPIiYTES 



wall pores, as has been demonstrated in Cycads and Conifers. 

 Just before fertilization, early in September, the small and 

 ephemeral ventral canal cell is cut off, and the large egg is organ- 

 ized (Fig. 34, C). Hirase states that about twenty weeks elapse 

 between pollination and the maturity of the egg. It should 

 also be noted that an archegonial chamber is developed in the 

 endosperm, as in Cycads, though this is somewhat modified later 

 by the remarkable development of an endosperm beak, to be 

 described in connection with fertilization. 



THE MALE GAMETOPHYTE 



Our knowledge of the development of the male gametophyte 

 of Ginkgo dates from Strasburger's account ^^ in 1892, much 

 extended by the recent very complete observations of Hirase ^^ 

 (Fig. 32). From this last account the following description of 

 the male gametophyte and of fertilization is derived. 



The first division of the microspore is unequal, resulting in 

 cutting off a small lenticular cell, which soon disorganizes and 

 later appears merely as a cleft in the heavy spore wall. This 

 first ephemeral cell may be regarded as a vegetative cell of the 

 gametophyte, a vestige of the vegetative tissue of a more exten- 

 sive and probably independent gametophyte. It is interesting to 

 note that this same ephemeral cell appears in the germination 

 of the microspores of most of the Conifers, but was not observed 

 by either Ikeno or "Webber in the Cycads. 



A second unequal division occurs, and a second small cell 

 IS cut off, which persists, and which represents a second vegeta- 

 tive cell (Fig. 32, A, p). This second vegetative cell is cut 

 off in the microspore of most Conifers, but it is ephemeral like 

 the first ; while this single persistent vegetative cell appears to 

 be^ the first and only one cut off in the microspores of Cycads. 

 GmJcgo resembles the Conifers, therefore, in having two vege- 

 tative cells ; and resembles the Cycads in having one persistent 

 vegetative cell. It is a question whether a first ephemeral vege- 

 tative cell may not yet be detected in Cycads, thus confirming 

 the close resemblance between these two grouiis which appears in 

 almost every other feature of their male gametophytes. 



After the t^vo vegetative cells have been cut off', the remain- 

 ing large cell is what we regard as the antheridium initial, whose 

 function is to organize the single antheridium. This cell di- 



