X THE HOMOSPOROUS LEPTOSPORANGIAT^ 357 



As in Onoclea the primary organs are established by the 

 first two walls, and the next divisions form octants, but there is 

 somewhat less regularity in the later divisions, in which respect 

 Osmunda is intermediate between the Polypodiacese and the 

 Eusporangiatse. As in the former, the two epibasal quadrants 

 develop stem and cotyledon, the hypobasal ones, root and foot. 

 At this stage the cells of the young embryo contain but little 

 granular cytoplasm, and there are large vacuoles. As the 

 embryo grows older the granular cell contents increase in quan- 

 tity. The subsequent divisions follow very closely those in the 

 embryo of Onoclea, but are less regular, and the embryo retains 

 for a longer time its original nearly globular form. 



Fig. 199.— Three sections of one embryo of O. cinnamomea in whicli tlie root (r) is 

 especially well marked, X260. Lettering as in the last. 



The direction of growth of the cotyledon is determined in 

 part by the first walls in its primary octants. The outer octant 

 usually becomes at once its apical cell, and if its first segment 

 is formed on the side next the octant wall, this throws the axis 

 of growth very much to one side, so that the axis of the, leaf , 

 may be almost at right angles to the median line of the embryo. 

 Otherwise it nearly coincides with this. The original three- 

 sided apical cell persists for a long time, and it could not be 

 positively shown whether or not it was afterwards replaced by 



