39 ^ West, — A Contribution to the Study of the Marcittiaceae . 
species (Text-figs. 25, A and B, 26, A and B, 27, A and b). At the apex of 
later roots of moderate size a block of about four equivalent initial cells is 
found (Text-fig. 28), but the largest and most bulky adventitious roots 
possess a definite apical meristem (Text-figs. 29, 30, A and b), consisting 
Text-fig. 26. Danaea nodosa , Sm. a and b. Longitudinal sections of small roots showing 
variation in shape of the single initial cell, x 180. 
Text- FIG. 27. Marattia Cooperi , Mre. A. Transverse section of the apex of a small root 
showing a single initial cell. B. Longitudinal section of the apex of a similar root showing the 
single initial cell, x 180. 
of a number of independent, usually wedge-shaped initials, which in median 
longitudinal sections of the roots in question appear to be arranged in a fan- 
shaped manner as described and figured by Campbell (20, p. 177, Fig. 162). 
Hence it would appear that in the case of the Marattiacean roots , the 
number of initial cells found at the apex depends upon the bulk, and 
