Betts. — AuteroJogii of Plants of Peridot if e Belt, Nelxo/i. 



145 



Anntomj/. 



Leaf. — The upper and the lower epidermis consist of more or less 

 rectangular cells with thin walls, except for the external ones, which 

 are slightly thickened. A thin cuticle is present. Stomates are equally 

 numerous on both surfaces ; the guard-cells are small, and level with the 

 surface. 



The chlorenchyma is differentiated. The palisade tissue consists of 

 3 layers of cells with thin walls, and containing numerous chloroplasts ; 

 these cells are closely packed together. The spongy tissue is composed of 

 more or less irregular thin-walled cells, forming a compact tissue with 

 only very small intercellular air-spaces. The chloroplasts are not nearly 

 as abundant in this tissue as in the palisadic. At intervals in the 

 mesophyll there are canals which are surrounded by a layer of epithelial 

 cells. Raphides of calcium oxalate are found in the mesophyll. 



Fig. 9. — Epilobium pedunculare. Transverse section of stem ( x 36). a, epidermis ; 



6, cortical chlorenchyma ; c, colourless cortex ; d, endoderrais ; e, phloem ; 



/, xylem ; g, pith with starch ; //, j^ith without starch. 

 Fig. 10. — Ejnlobiiaii pubens. Transverse section of stem (x 36). a, epidermal hair; 



b, cortical chlorenchyma ; c, colourless cortex ; d, endodermis ; e, phloem ; 



/, xylem ; g, pith with starch ; h, pith without starch. 



The vascular bundles are small, and contain only a small amount of 

 lignified tissue. Below the midrib there are small more or less rounded 

 cells, which contain a very few chloroplasts. This forms a water-tissue. 

 In the vicinity of the vascular bundles the lower epidermal cells are smaller 

 and have thicker walls. 



Stem (fig. 9). — The epidermis is composed of small cells, which in trans- 

 verse section are squarish or round. These cells have thickened walls, and 

 there is also a cuticle, which is, however, only thin. Some of the epidermal 

 cells are produced into thin-walled unicellular hairs, which contain proto- 

 plasm. Stomates are present, but are not numerous ; the guard-cells are 

 small, and level with the surface, as in the leaf. 



The cortex forms a fairly wide band, about 9 cells wide. The outer 

 portion consists of small cells with thickened walls, and containing a few 

 chloroplasts. The inner part of the cortex consists of larger roundish or 

 polygonal thin-walled cells which are compactly arranged, so that there 

 are only very small air-spaces. These cells contain starch-grains. The 

 endodermis is well defined ; it consists of a single layer of large oval 

 or rectangular cells with suberized walls. 



