No. 526] SEXUAL REPRODUCTION IN GYMNO SPERMS 



of Pinus. Oogenesis does not cover so great a range, 

 for motile eggs are not found above the thallophytes. 

 In its most primitive condition, the archegonium of the 

 gymnosperms is more reduced than any found in pteri- 

 dophytes, for there is no neck canal cell. An egg with a 

 definite ventral canal cell, as in Ginkgo and Punts, is the 

 most primitive condition found in gymnosperms. Be- 

 yond this there is the elimination of the wall between 

 the ventral canal nucleus and that of the egg, as in 

 cycads and many conifers, a natural step in the elimina- 

 tion of the ventral canal nucleus, and in Tor rain, even 

 the nuclear division has probably failed to take place, 

 so that the central cell functions directly as an egg. A 

 still further reduction is found in Turn boa where the 

 incomplete septation of the female gametophyte results 

 in a failure to organize a definite egg; and finally, there 

 is a complete suppression of any septation whatever, so 

 that the egg is represented only by a nucleus with as 

 little organization of cytoplasm about it as can be found 

 in any angiosperm. Thus there lias been a gradual re- 

 duction of the archegonium from a condition almost like 

 that of the pteridophytes to the most extreme condition 

 found in angiosperms. 



Some might suggest that such reductions would have 

 their natural termination in the elimination of all sexu- 

 ality, with apogamy as the goal. In Gnetum Ule there 

 seem to be instances of apogamy. In the cases reported 

 as apogamy in Pinus there is the possibility of fertiliza- 

 tion by the ventral canal nucleus. Personally, I prefer 

 to regard apogamy as a specialized, unnatural phenom- 

 enon, and not as a condition toward which plants are 



The behavior of the chromatin in the final stages of 

 both spermatogenesis and oogenesis in gymnosperms 

 seems to be unique. At the formation of the ventral 

 canal cell or ventral canal nucleus, the chromosomes are 

 very small. The ventral nucleus or cell soon disinte 

 grates, but the chromosomes of the egg nucleus form a 

 spirem. From this point there is a period of develop- 



