104 BOTANICAL GAZETTE [February 



leaves. On rosette leaves the hairs are slightly more abundant 

 on the upper than on the lower surface, and gradually diminish in 

 size and number toward the basal leaves. On the lower side of the 

 basal leaves there are very few hairs except along the margin, 

 where they are long and abundant. The chlorenchyma contains 

 an abundance of needle-shaped crystals of calcium oxalate, arranged 

 in bundles (raphides) . These raphides are slightly more abundant 

 iu rosette than in stem leaves. 



Verbascum Blattaria. — In this species the palisade tissue is 

 best developed in the floral leaflets and in the upper stem leaves. 

 Here the layers are well organized and compact, and the cells 

 reach their maximum length. In the basal stem leaves the palisade 

 cells vary considerably in length, some being quite long, while 

 others are quite short. Moreover, the layers are poorly organized. 

 In the middle and upper stem leaves 3 layers are well organized, 

 a fourth layer being only partly organized. In the basal leaves 

 there is no trace of a fourth layer. The thickness, or transverse 

 diameter of the palisade cells, also increases appreciably from the 

 upper to the lowest stem-leaves. In rosette leaves there is a grad- 

 ual increase in the size of palisade cells from the upper to the basal 

 leaves. In the latter the palisade tissue is poorly developed, the 

 cells being very irregularly and loosely arranged, and scantily 

 supplied with chloroplasts. 



With the exception of a few hairs on the ribs of rosette leaves and 

 lowest stem leaves, this plant is devoid of hairs. The basal stem 

 leaves and rosette leaves have the largest epidermal cells, which 

 also have the largest vertical diameter. The upper epidermal cells 

 of both stem and rosette leaves always have a decidedly greater 

 vertical diameter than the cells of the lower epidermis. 



The floral leaflets and upper stem leaves have the thickest outer 

 epidermal wall and cuticle. In these leaves there is very little 

 difference between the upper and lower epidermis. In the upper 

 rosette leaves we also find a thicker epidermal wall and cuticle, 

 but the difference is less pronounced than in stem leaves. 



A summary of the comparative study of the upper, middle, 

 and lower stem leaves and the corresponding upper, middle, 

 and lower rosette leaves, based upon the 5 species just considered, 







» 



