XI 



THE HOMOSPOROUS LEPTOSFORANGIATJ-: 



349 



quadrants, and the organs derived from them, are situated Hkc 

 those of the polypodiaceous embryo, with reference to the 

 prothallium, but not to the archegonium. 



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 Polypodiaceae and the 

 Eusporangiatae. As in the former, the two epibasal quadrants 

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

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



Fig. 177. — Three sections of one embryo of O. cinnainomea in which the root (?•) is especially well 



marked, X260. Lettering as in the last. 



granular cytoplasm, and there are large vacuoles. As the 

 embryo grows older the granular cell contents increase in 

 quantity. 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. 



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 

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

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

 of the leaf may be almost at right angles to the median line of 



