1907] LAND— EPHEDRA TRJFURCA 2S1 



the gametophyte is stimulated to further activity. A single plate of 

 the outermost layer of cells of the gametophyte, forming the bottom 

 of the pollen chamber and extending outward a short distance under 

 the tip of the nucellus, becomes meristematic {]ig. 2j), and by repeated 

 periclinal and a few anticlinal divisions forms a plug which effectually 

 closes the poren chamber and receives the backward thrust of the 

 elongating cells of the gametophyte and later of the embryo; this plug 

 persists until absorbed by the maturing embryo. The antipodal 

 region begins active division and the bulk of the gametophyte is 

 materially increased. The cells near the archegonia first elongate, 

 followed successively by groups of cells extending across the gameto- 

 phyte. The elongated cells after having lost their contents are folded 

 back and forth in the micropylar region (fig. ^5), being prevented 

 from escaping through the pollen chamber by the pollen-chamber 

 plug- This elongation of groups of cells, proceeding successively 

 from the micropylar to the antipodal region, serves admirably to keep 

 an abundance of food constantly near the embryo. 



matures 



t> 



wath food. The epidermal cells, especially those of the nucellus, are 

 filled with starch and become so turgid that they are frequently torn 



from the layer beneath (fig 



May 



of yoiing plants were escaping from strobili still attached to the stem. 

 This shows that under conditions favorable for growth the period of 

 rest of the seed of E. trijurca is a brief one, if indeed it has a rcsting- 

 period. 



Staminate and ovulate strobili were first recognized in December, 

 but they had probably been set the preceding month and perhaps 

 earlier. The time from the setting of the strobili to the ^^germina- 

 tion'' of the seed is therefore approximately six months. Compared 

 with pines the time is short, for the latter require about thirty-six 

 months. 



DISCUSSION 



pound 



to all Gnetales and shared by the Coniferales. The staminate 

 strobilus, as in other Gnetales, is also compound, a character not found 

 in other gymnosperms. Perhaps the nearest approach to a com- 



