308 Schivcly — Contributions to the Life History of 



angle of 45 ° to 6o°. The pulvini of the leaflets stand up 

 at an angle of 30 with the petiole, so that the surface of 

 the blades lie about in the same plane. 



Histology of the Leaf. 



The epidermal cells are irregular, stomata occur upon 

 both surfaces of the leaf, but are much more numerous 

 upon the lower than upon the upper. Large firm unicel- 

 lular hairs are placed at regular intervals upon both sur- 

 faces and are exceedingly numerous upon the margins, par- 

 ticularly of young leaves. These hairs are thick-walled 

 and bear tubercle-like markings. On the midvein, on 

 some of the larger veins, and on the margin are found small 

 bladder-like hairs. 



The vascular bundles branch extensively; but frequently 

 there is no evidence of anastomosing. This is often seen 

 with the more delicate branches, which suddenly terminate 

 in the mesophyll. Embedded in the larger vascular areas 

 (probably in all, however) have been seen crystals similar 

 to those occurring in the clearly defined crystal sheath, 

 previously described in the stem. Possibly, however, 

 because they are not so massed up on one another, their 

 distinct twin-like structure is much more easily distin- 

 guished, the partition, whether apparent or real, being 

 easily located. (Plate XXIV., Fig. 5.) 



The transverse section shows thin upper and lower 

 epidermal layers, while the mesophyll consists of irregular, 

 but tolerably uniform cells, so that a differentiated palisade 

 tissue is absent. 



Simple and compound leaves correspond in the above 

 details. 



Leaf Positions. 



In common with many other members of the Leguminosae, 

 Amphicarpiea is exceedingly susceptible to changes in tem- 

 perature, moisture and light. Because of the delicate foliage, 

 many difficulties arise, and constant watchfulness is neces- 

 sary to explain the condition of each plant. 



