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GEO. S. BRYAN 
questionable. Cell a in figure 4 suggests such a possibility. The elongation 
of this cell together with the size of the nucleus makes it seem probable 
that such a division is about to take place. 
While it is impossible to trace with absolute certainty all of the divisions 
undergone by the basal cell, a study of basal regions shows two distinct 
types of divisions (figs. 2-21). As illustrated by figures 3, 8, 9, 11, and 12, 
Fig. 15. Embryo showing 10 primary segments. Basal portion of sporophyte 
slender and without irregular divisions. FiG. 16. Bulbous type of young embryo. Cells 
of basal portion have strong tendency to round away from each other. Fig. 17. Embryo 
showing probably 9 primary segments. Basal portion bulbous. All X 300. 
the basal cell divides irregularly, while in the embryos shown in figures 
6, 7, 13, 14, and 15, if the basal cell has divided the divisions are regular, i.e., 
brought about by walls parallel to that first formed. This irregularity or 
regularity expresses itself later in what might be termed two types of young 
sporophytes. The first of these, in which the lower portion is distinctly 
bulbous, is derived from the irregular type. The cells formed by these 
irregular divisions grow considerably in size and tend to round away from 
each other (figs. 16-17). Such embryos stand in sharp contrast to those of 
