162 MORPHOLOGY OF SPERMATOPHYTES 



jacket cells about the central cell, whicli through numerous wall 

 pores empty their contents, nuclei and all, into the rapidly 

 enlarging central cell, and this material remains conspicuous 

 in the large egg. The neck is quite variable in structure, 

 organizing from two cells to several tiers with eight cells in 

 each tier. Probably the most common structure is two tiers 

 with four cells in each tier. The two-celled neck, so far as re- 

 corded, occurs in Cycadales, Ginkgoales, Tsuga Caiiadensis, and 

 CepJialotaxus Fortunei. Tumboa and Gnetum develop no arche- 

 gonia, as would be expected from the nature of their endo- 

 sperm tissue. In Tumboa the archegonium initials are selected, 

 but no division occurs, the egg organizing directly in the initial ; 

 while in Gnetum the eggs are as free and naked as in the Angio- 

 sperms. The last two forms are particularly suggestive in 

 representing the possible method of transition froni a compact 

 ante-fertilization endosperm to one that consists of free nuclei 

 when fertilization occurs, a very characteristic feature of Angio- 

 sperms. 



THE MALE GAMETOPHYTE 



While information concerning the germination of the micro- 

 spores of Gymnosperms is still very much needed, enough has 

 been observed to indicate the general character of the game- 

 tophyte. In most cases one or two vegetative (" prothal- 

 lial ") cells are first cut off. In Cycadales a single such cell 

 is cut off and persists; in Ginkgoales and Ephedra two siich 

 cells are successively cut off, the first being ephemeral ; while in 

 Abieteae two cells are cut off, and both are ephemeral. In cer- 

 tain forms studied, as Taxus, Juniperiis, Cupressus, and Se- 

 quoia, no evidence of vegetative cells has been obtained. It 

 should be remembered, however, that these cells are cut off rap- 

 idly and are very ephemeral, so that traces of them may be lost 

 quickly, or they may easily escape observation. "We venture 

 the opinion, therefore, that one or two vegetative cells, more or 

 less evanescent, will be found to be of common occurrence among 

 Gymnosperms — cells which are almost imknown among Angio- 

 sperms. 



The large cell which remains after the cutting off of the 

 vegetative cells we have taken to be the morphological equivalent 

 of the antheridium initial as it appears in the heterosporous 



