1 8 Russell—Comparison of the Structure of Hybrid 



xylem. The things especially to be noted in comparing parents 

 and hybrids are: the number of the subepidermal layers of 

 cells, the depth and character of the mesophyl tissue, the rela- 

 tive amount of sclerenchymatous tissue developed on the 

 inner and outer side of the bundles, the number of subdetentive 



layers. 



In all three forms, the outer epidermal cells are regular with 

 heavily cutinized walls. The stomata have their guard cells 

 slightly raised above the epidermal level. 



Below this are the subepidermal layers of cells rich in chloro- 

 plasts, forming on the morphologically lower surface a false 

 palisade. In S. purpurea there are 3-4 layers of cells, large 

 and thin-walled. In S. flava there are 4-5 layers of these cells. 

 They are smaller and more compactly arranged. 5. Catesbaei 

 resembles more S. purpurea in that there are three subepidermal 

 layers, which have larger cells less compactly arranged than in 

 S. flava. 



The mesophyl is in 6". purpurea deep and loose. The cells 

 are large, and intercellular spaces are frequent. S. flava has 

 a very narrow mesophyl zone. The cells are regularly arranged 

 with few intercellular spaces. In S. Catesbaei the mesophyl 

 is deep and spongy as in S. purpurea. In the mesophyl the 

 bundles are distributed. In 5. purpurea they are not strongly 

 reinforced with sclerenchyma tissue. In 5. flava the rein- 

 forcement is pronounced, and involves the subepidermal and 

 epidermal layers as well in the larger bundles. In 5. Catesbaei 

 the development is about intermediate between the parents. 



There are two or more layers of cells below the detentive 

 surface which are thickened together with the epidermis. It 

 is this which forms the so-called "absorption zone" mentioned 

 by Fenner (31) and others. The contents of these cells are 

 either gathered into large masses, or broken up into finely 

 granular substance. These layers give a strong positive reac- 

 tion for tannin. In 5. purpurea there are 1-2 layers of sub- 

 detentive cells. In S. flava there are two layers. In 5. Cates- 

 baei there are three layers. 



Set 2. S. flava, S. Drummondii and S. Moorei 



The second hybrid of the series, between 5. flava and S. 

 Drummondii, was the first artificial hybrid between species 

 of Sarracenias to be exhibited. Though it was named in honor 



