140 



THE MARATTIALES 



the stem and cotyledon can be recognized, although the embryo still retains its oval 

 outline. As in the embryo of Marattta, growth is most active in the central region 

 of the epibasal part of the embryo and there can generally be recognized a large 

 central cell, which is presumably the single initial of the stem apex, although, as 

 in the case of Marattia, it is not absolutely certain that a single initial cell is always 

 present. Cell division is especially active on one side of the stem apex, and this 

 area marks the position of the young cotyledon. The limits of this growth area are 



Fig. Ill 



A. Two longitudinal sections of an old embryo of Angiopteris. X75 



B. Stem region of same embryo. X160. 



C. Root apex. X160. 



not very sharply defined and it is difficult to say whether it can be traced back to 

 a single quadrant or octant cell, but it is probably not always constant in its 

 position; indeed, the stem looks as if the stem apex and the cotyledon both arose 

 from the same quadrant, the second epibasal quadrant contributing, at least in 

 part, to the foot. 



As seems to be true in all the Marattiaceae, the root makes its appearance at a 

 comparatively late period and it is evident that the root, as in the embryo oi Marattia, 

 is a strictly endogenous structure. The first indication of the root is the development 



Fig. 112. 



A. Longitudinal section of an advanced embryo of Angiopteris^ cut in the plane of the lamina of the cotyledon. X50. 



B. Cotyledon of same embryo, showing dichotomy of apex. X220. 



C. Root apex of same. X220. 



of a group of actively dividing cells, almost in the center of the embryo below the 

 stem apex. This meristematic region is probably always of epibasal origin, but it is 

 close to the basal wall and it is possible that sometimes it may arise below it. The 

 apical cell, which in the early stages almost always appears triangular in section, 

 becomes conspicuous and was recognized by Farmer in his study of the embryo of 



