MACROSCOPIC AND MICROSCOPIC CHARACTERS OF PLANTS. 



795 



TABLE J 19. Continued. 



The two layers of aqueous tissue beneath the upper 

 epidermis have thin cells lengthened at the midrib angle, 

 the first layer being particularly noticeable. The cells 

 of the first layer are much longer in C. mossice than in 

 L. purpurata, and those of the hybrid are about as long 

 as those of C. mossice. (Table J 19.) 



The lower epidermis consists of rather thick-walled 

 cells which at the midrib angle are deeper than wide. 

 The lower epidermis of C. mossice is deeper than that of 

 L. purpwata, but that of the hybrid is not as deep as 

 those of the parents. The cuticle on the lower epidermis 

 is of the same depth in the hybrid as in L. purpurata, 

 both being of greater depth than in C. mossice. (Table 

 J19.) 



Beneath the lower epidermis at the midrib in L. pur- 

 purata is one layer of cells which is not different from 

 the layers beneath it, excepting for the slightly smaller 

 size of the cells. In C. mossice there are two distinct 

 layers of oval cells longer than deep and smaller than 

 the other cells, and arranged more closely together. In 

 the hybrid there is one distinct layer of closely packed 

 oval cells and a layer of cells beneath, which are a little 

 smaller than those of the underlying layers. (Table 

 J19.) 



The midrib bundle is much larger in L. purpurata 

 than in C. mossice and is smaller in the hybrid than in 

 either parent. Lowermost in this bundle is a somewhat 

 crescentic area of heavily thickened cells, the scler- 

 enchyma. This is just twice as thick in L. purpurata 

 as in C. mossice and the hybrid. Just above this is a 

 small patch of phloem which is smaller in L. purpurata 

 than in C. mossice, and smaller in the hybrid than in 

 either parent. Above this is an area of xylem consisting 



of thick-walled cells, which area is larger in L. purpurata 

 than in C. mossice and smaller in the hybrid than in either 

 parent. (Table J 19.) 



Examined at the first main vein from the midrib, the 

 upper epidermis appears as a layer of thick-walled, rec- 

 tangular cells, slightly rounded at the angles, and with 

 a thick cuticle on the outer face. The cells of L. purpu- 

 rata are larger than those of C. mossice, while those of the 

 hybrid, though of the same depth as those of C. mossice, 

 are not so wide as in the parents. The cuticle of the 

 hybrid is in depth exactly mid-intermediate between the 

 depths of the parents. (Table J 19.) 



Beneath the upper epidermis is a layer of oval rec- 

 tangular cells and beneath this a layer of rather irregu- 

 larly shaped cells, both layers containing very few chloro- 

 plasts. These compose the aqueous tissue. The cells of 

 the first layer beneath the epidermis are larger in L. pur- 

 purata than in C. mossice, and in the hybrid, though 

 between the parents in width, the depth is less than that 

 of either parent. (Table J 19.) 



The cells of the lower epidermis are much wider than 

 deep in L. purpurata, and slightly wider than deep in C. 

 mossice and the hybrid, but the difference between width 

 and depth is so small that they appear almost square. The 

 cells of the hybrid are in size between those of the parents 

 though very near C. mossice. They are thick-walled like 

 those of the upper epidermis, and provided with a thick 

 cuticle on the outer face, which latter in the hybrid is 

 exactly mid-intermediate in depth between those of the 

 parents. (Table J 19.) 



Just beneath the lower epidermis is a layer of oval 

 cells which are more closely packed than the underlying 

 cells. These oval cells are larger in L. purpurata than in 

 C. mossice, and in the hybrid, though between the parental 

 sizes, they are slightly nearer L. purpurata in depth but 

 much nearer C. mossice in width. (Table J 19.) 



Beneath the upper epidermis and the aqueous tissue 

 are layers of elongated palisade cells which are thin- 

 walled and contain green chloroplasts, and which store 

 mucilage and starch. Beneath the palisade cells is the 

 spongy mesophyll, composed of large, rounded, thin- 

 walled cells. They contain green chloroplasts and store 

 mucilage and starch. Embedded in the palisade tissue 

 are strands of sclerenchymatous tissue arranged in a row 

 beneath the upper epidermis (1.6 mm. objective). These 

 strands are present in the same number in L. purpurata 

 and the hybrid, but smaller in the hybrid than in L. pur- 

 purata. They are entirely absent in C. mossice. In L. 

 purpurata 3 to 4 strands, diameter 66.2/u; in C. mossice 

 no strands; in L.-C. canhamiana 3 to 4 strands, 54.7/i 

 in diameter. 



There is another row of sclerenchymatous strands 

 embedded in the spongy mesophyll along the lower epi- 

 dermis. These are more numerous in L. purpurata than 

 in C. mossice. The number in the hybrid is between 

 those of the parents, but nearer that of L. purpurata, 

 and the strands are smaller than in either parent. In 

 L. purpurata 6.9 strands in a field, 66.9/x in diameter; 

 in C. mossice 4.9 strands in a field, 55. 1/*, in diameter; in 

 L.-C. canhamiana 6.4 strands in a field, 47.9/t in diameter. 



The bundle is essentially the same as that of the mid- 

 rib, except that the sclerenchymatous sheath on the lower 

 side is not so well developed. 



