268 MORPHOLOGY OF GYMNOSPERMS 



may be only one tier or more than two tiers, more than four cells in 

 each tier are known to occur, in some cases there are only two cells 

 in a tier, and in Tsuga canadensis (37, 60) the neck is frequently 

 two-celled, but often consists of three or four cells. It should be kept 

 in mind that a two-celled neck is a feature of Cycadales and Gink- 

 goales, and for that reason it has been assumed to be the primitive 

 type of neck. So far as we have observed, however, there is no typical 

 number for neck cells, the two-celled neck occurring indiscriminately 

 among Pinaceae, the number of cells developing apparently holding 

 no definite relation to phylogenetic connections. A notable feature 

 of the Abietineae is the formation of a true ventral canal cell, a dis- 

 tinct wall plate cutting it off from the egg. This is true only of the 

 Abietineae among conifers; and if the elimination of the separating 

 wall plate, resulting in the ventral canal cell being represented only 

 by its nucleus, is an evidence of a further stage in the reduction of the 

 axial row, the Abietineae are the most primitive conifers in this charac- 

 ter. Even among them, as mentioned above, occasionally the wall 

 sometimes disappears, leaving the ventral nucleus free. 



Among the Taxodineae the number of archegonia ranges from 

 four to sixty (4-6 in Sciadopitys, 8-15 in Cryptomeria, 10-35 i^ Taxo- 

 dium, 60 in Sequoia sempervirens) , which is the largest range among 

 Pinaceae. The number of neck cells ranges from two to eight 

 (Sequoia 2 and occasionally 4, Taxodium 2-6 or more, Cryptomeria 

 usually 4, Sciadopitys 4-8), forming a single tier. The neck cells of 

 Sciadopitys are peculiar in being vertically elongated. In Sequoia 

 sempervirens Lawson reports (92) that the very numerous arche- 

 gonium initials are differentiated deep in the endosperm of the 

 micropylar region, and that the necks are pushed to the periphery 

 of the endosperm by the elongating central cells, being directed 

 toward the nearest pollen tubes, which have taken their positions 

 before the archegonia were formed (92). It is in Cunninghamia 

 (147, 180) that the archegonium initials appear very early in the 

 ontogeny of the gametophyte. A significant feature in connection 

 with the archegonia of this tribe is their grouping, in some genera, 

 into what may be called an archegonium complex. This means that 

 the archegonia are grouped in contact, invested by a common arche- 

 gonial jacket, and with a common archegonial chamber. Since 



