256 UNIVERSITY OF COLORADO STUDIES 



Carruthers, the assistant director, for their uniform courtesy. While at 

 the gardens I secured a large amount of other material which I hope to 

 study in the not far-distant future. 



Jatropha curcas Linn. 



General. — Most of the Euphorbiaceae have foliaceous cotyledons 

 but the leaf-like appearance of the cotyledons in this species is particu- 

 larly well marked. A large lamina is developed which is broadly ovate 

 with heart-shaped base. It reaches a length of 60 mm. and a width of 

 50 mm. The cotyledons do not resemble the leaves in form or in vena- 

 tion but the texture is much the same. The foliage leaves are palmately 

 veined and somewhat the shape of a maple leaf. The sinuses are shallow. 

 Jatropha curcas is a shrub or small tree. A full account of the external 

 features of the seedling is given by Lubbock. 1 



Epidermis as seen in surface view. — The cotyledons and leaves have 

 a similar epidermis, the cells only slightly wavy in outline. In both 

 structures the cells of the upper surface are larger than those of the lower 

 surface. Both faces of the cotyledon have stomata. In the leaf, 

 stomata are very few on the upper surface but numerous below. 



Internal structure. — Very little difference is to be seen in vertical 

 sections of expanded portions of cotyledon and leaf. A well-developed 

 palisade -occurs in both, but the cells of this are larger in the leaf than in 

 the cotyledon. 



Cotyledon stalk and leaf petiole. — Here very marked differences 

 occur. The vascular tissue of the cotyledon stalk is in the form of an 

 interrupted arc composed of about seven bundles. In the leaf petiole, 

 on the other hand, the vascular tissue forms a hollow cylinder just as in a 

 stem, and even in a very young petiole a large number of bundles may be 

 counted, arranged in an interrupted circle. 



Manihot glaziovii Mull. Arg. 



General. — This Euphorbiaceous tree furnishes "Ceara rubber." 



The cotyledons are distinctly foliaceous but very different from the 



leaves in shape and venation. The lamina is oblong and notched at 



the base instead of being palmately lobed as is the case with the leaf. 



1 Lubbock, Seedlings. 2:484. 1892. 



