328 GYMNOSPERMS 



burger's correction of the mistake, perhaps because Strasburger 

 was 20 years younger. 



The primary neck cell early undergoes an anticlinal division, and 

 a second anticline makes a plate of four cells. Later, there is usually 

 a pericline, making two tiers of cells. In each tier there may be two 

 divisions, so that the neck of the archegonium consists of eight cells. 

 One or more of these mitoses may fail to take place, so that the 

 number is usually less than eight. Occasionally, there are more than 

 two tiers, and occasionally only one. In Podocarpus coriacca,^*" the 

 number is variable, ranging from 2 to 25. In Tsuga canadensis ,*°*' ""^ 

 there is only one tier, and it may be only two-celled. Austrotaxus*'^^ is 

 exceptional in having as many as 16 neck cells, all in one tier. 



There is no neck canal cell in any gymnosperm. In the evolution 

 of the archegonium the neck canal cell made its final appearance in 

 the heterosporous pteridophytes, all of which have a single small 

 neck canal cell. 



The division of the central cell to form a ventral canal cell, or 

 nucleus, and the egg, occurs shortly before fertilization, so that the 

 development of the egg is almost entirely the development of the 

 central cell. In the Abietaceae there is a distinct ventral canal cell 

 (fig. 323). In the rest, there is a nuclear division, but no wall is 

 formed between the two resulting nuclei. It is a curious fact that 

 those in which no wall is formed between the two nuclei are the ones 

 in which the sperms are distinct cells. In Pinus, with a distinct ven- 

 tral canal cell, the sperm has become reduced to a naked nucleus. 



In Pinus, the ventral canal figure is usually small, cutting off a 

 small ventral canal cell which promptly degenerates (fig. 323^1,^). 

 Occasionally, the figure is comparatively large, and cuts off a large 

 ventral canal cell (fig. 323 C,E). When a large cell is cut off, it 

 sometimes happens that the wall between the two nuclei breaks 

 down. The ventral canal nucleus, then being surrounded by the 

 general mass of the cytoplasm of the egg, grows and equals the egg 

 nucleus in size and, apparently, in development. It might be ferti- 

 lized, or it might fertilize the egg (fig. 323 £). Hutchinson' 'S 

 observed both these cases in Abies balsamea. 



Land"7 found cases in Thuja occidentalis which led him to believe 

 that both the egg and the ventral canal nucleus had been fertilized, 



