A STUDY OF CERTAIN FOLIACEOUS COTYLEDONS 259 



sion of the epidermal cells of the cotyledon ever occurs, I do not know. 

 Such division does not appear in any of my sections. The upper epider- 

 mis is relatively thicker in the leaf than in the cotyledon. Both struc- 

 tures have a one- layered palisade; but in the leaf the cells below this are 

 somewhat elongated vertically so that one might almost call this a two- 

 layered palisade. The spongy parenchyma of the cotyledon consists 

 of about five layers of cells while in the leaf there are only about three. 

 Cotyledon stalk and leaf petiole. — Four large vascular bundles are 

 found in the leaf petiole. They are arranged with phloem outside in 

 a continuous ring. In transverse section the xylem area has the form 

 of a Maltese cross. Only a single broad, flat vascular bundle is found 

 in the cotyledon stalk and the stalk is much flattened dorso-ventrally, 

 being concave above and convex below. 



COUROUPITA GUIANENSIS AuU. 



General. — This is the "cannon ball tree," cultivated in the tropics, 

 and well known for its wealth of dark red flowers, produced on small 

 branches of the main trunk and followed by the large, smooth, spherical 

 fruits. It belongs to the family Lecythidaceae. The cotyledons 

 resemble the leaves very closely in shape and venation. In fact, this 

 plant affords the only example I know in which the cotyledons really 

 are closely like the leaves. 



Epidermis as seen in surface view. — The epidermal cells of both 

 leaf and cotyledon are wavy in outline. Apparently no stomata occur 

 on the upper surface of either, although present on the lower surface in 

 both. A given area of leaf has a greater number of stomata than the 

 same area of cotyledon. The nuclei of the epidermal cells of the coty- 

 ledon are very prominent. 



Internal structure. — The leaf palisade is well marked and consists 

 of a single layer of cells. About five layers of cells go to make up the 

 spongy parenchyma. The cotyledon has what looks like an incipient 

 palisade above a large-celled spongy parenchyma. The palisade layer 

 has somewhat the appearance of that in young leaves, but the cells 

 are of different shape, peing pointed below. Hence, the palisade of 

 the cotyledon cannot be said to show a mere case of arrested develop- 



