166 



THE MARATTIALES 



cap are cut off from them. The outer cells of the root cap are very much enlarged 

 and there is an evident space between the root and the surrounding tissues. The 

 trace from the third leaf joins that of the second one close to its union with the 

 bundle from the cotyledon (fig. 148, 5). 



In fig. 150 are shown nine cross-sections from a series made from a plant of Z). 

 jamaicensis, in which four leaves were evident. A microscopic examination of the 

 stem apex showed, however, that a fifth leaf was also present, which stood nearly 

 directly opposite the cotyledon. A shows sections only of leaves 3 and 4, the latter 

 having the stipules conspicuous, while these are absent or scarcely developed at all 

 on the first three leaves, at least in the specimen in question. Between the leaves 

 are seen sections of the numerous scales which beset the surface of the young leaves. 

 B is taken somewhat lower down and includes a section of leaf 5. C passes through 

 the stem apex and shows clearly the spiral arrangements of the first five leaves, 

 each of which has in its petiole a single concentric bundle which becomes larger in 



1 iG. 150. — D. jamaicensis. 



Series of transverse sections of a young sporophyte, with three fully-developed leaves and two younger ones. X20. 

 Section C passes through the stem apex. Roman figures indicate successive leaves. 



each successive leaf, with a corresponding increase in the development of the xylem. 

 As the sections are examined, farther and farther down in the stem (D to F), one 

 can see very clearly the way in which the single bundle in the lower part of the 

 stem owes its origin to the coalescence of the leaf traces. Proceeding downward 

 the traces of leaves 4 and 5 are seen to approach gradually and finally to become 

 completely coalescent; and still further down {F) the leaf trace from 3 joins that 

 from 4, and a single bundle results, crescent-form in section, but showing clearly its 

 compound nature. The three xylems never become entirely confluent. 



