A STUDY OF CERTAIN FOLIACEOUS COTYLEDONS 257 



In the seed the blade of the cotyledon is 12 mm. long; it grows to be 

 45 mm. 



Epidermis as seen in surface view. — So far as my observations go it 

 seems that there is no essential difference in the epidermis of the coty- 

 ledon and leaf. All the cells have a somewhat wavy outline. Both 

 surfaces of the leaf and cotyledon are provided with stomata. 



Internal structure. — Here, again, the two organs are much alike. In 

 fact, save for the somewhat larger size of cells in the cotyledon they can 

 hardly be distinguished in cross section unless attention be paid to the 

 vascular tissue. Both are quite thin. They have a single layer of 

 palisade and about five layers of cells forming the spongy parenchyma. 



Cotyledon stalk and leaf petiole. — In these there are marked differ- 

 ences. The cotyledon stalk is flattened and there are but two vascular 

 bundles. A well-developed endodermis extends around the outer, or 

 under, surface, forming about three quarters of an ellipse. Parallel to 

 this is a layer of cells with dark brown contents. Five vascular bundles 

 are found in the leaf petiole, which is nearly cylindrical and the endo- 

 dermis extends the whole way around accompanied by the layer of cells 

 with dark contents. 



Eriodendron anfractuosum D.C. 



General. — This species is known as the "white cotton tree" or "silk 

 cotton tree." It belongs to Bombacaceae. The cotyledons are strikingly 

 leaf-like in appearance. They increase in size after opening and carry 

 on all the assimilatory work of the plant for some time. The foliage 

 leaves are slow in appearing. These are palmate and the leaflets are 

 very different from the cotyledons. I give no drawing of this seedling 

 as a good figure is printed by Lubbock. 1 



Epidermis as seen in surface view. — Stomata are found only on the 

 lower surfaces of both cotyledon and leaf; they are far more numerous 

 on the leaf. Distinct reticulate thickenings of the outer epidermal walls 

 are present on the lower leaf surface but absent from the corresponding 

 area of the cotyledon. The upper surfaces of both structures have 

 slightly thickened wavy lines. 



1 Lubbock, Seedlings. 1:261. 1892. 



