[Vol. 9 

 90 ANNALS OF THE MISSOURI BOTANICAL GARDEN 



the spores about the bases of the still active leaves, from which 

 material for study of the gametophyte stages may be drawn. 



The microspore upon germination gives rise to a small len- 

 ticular cell at one end, which has been called the prothallial cell. 

 The remaining cell, the antheridium initial, divides in such 

 fashion that a single wall-layer is formed, investing a central 

 region of four cells, each one of which produces a large multi- 

 ciliate, spirally coiled sperm (Belajeff, '85). 



The megaspores, well filled with storage material of starch and 

 oil, are reported by Campbell ('91) as undergoing free nuclear 

 division to the number of 30-50 nuclei, when division walls begin 

 to appear at the apical end, later along the margin of the spore, 

 and eventually in the central portion. There is some increase in 

 size with development, as a rule, so that there is cracking along 

 the three ridges converging at the apex. It is in this region that 

 the archegonia develop, so that three lines of these up to the 

 number of thirty can be observed, if fertilization is prevented. Ac- 

 cording to Campbell, the archegonium initial divides trans- 

 versely, giving rise to the cover cell (later producing four tiers of 

 neck cells) and the inner cell (later dividing into the neck canal 

 and the central cell). The neck canal nucleus divides, but ac- 

 cording to Campbell, no wall is produced and it remains a short 

 wide cell. In other species, a longitudinal wall has been reported 

 by Miss Lyon and Arnoldi. The central cell divides to produce 

 an egg and a ventral canal cell quite as broad as the egg. 



When mature, the archegonium shows the usual canal to the 

 egg, due to disintegration of the canal cells, which allows the 

 entrance of sperms and the subsequent fertilization of the egg. 

 In the development of the embryo, the first stage (Campbell) 

 is transverse division into two cells, followed by a quadrant stage 

 in the most regular cases. The two lower quadrants are reported 

 as giving rise to the foot, one of the upper to a leaf and one to a 

 root. Later, a stem tip develops between the leaf base and the 

 root, in such manner that its origin may be from either. Very 

 early in the development of the leaf rudiment, the ligule cell 

 begins its activity. Division of cells and elongation is rapid 

 in all regions, so that the stages pass quickly. The embryo 

 sporophyte soon projects beyond the gametophyte, a second leaf 

 is formed and a second root. Meanwhile, there is tissue differen- 

 tiation; the vascular elements of the leaf, stem, and root are 



