238 Transactions. 



The chlorenchyma is differentiated. The palisade tissue consists of about 

 5 layers of somewhat irregular cells. These cells are very large and are com- 

 pactly arranged, so that there are only small intercellular air-spaces. The 

 cells contain a large number of small chloroplasts. 



The spongy tissue is composed of very large thin-walled more or less 

 rounded cells, with a thin peripheral layer of protoplasm in which are 

 embedded the small chloroplasts. This tissue is for water-storage. There 

 are frequent air-spaces in it, but they are small compared with the size of 

 the cell. 



The vascular bundles are small, and are surrounded by a sheath of paren- 

 chymatous cells which have thin walls and which contain a few chloroplasts. 

 The xylem and the phloem are of the usual type. The amount of lignified 

 tissue is small. 



Stem (figs. 7-8). — The epidermis consists of small somewhat dome- 

 shaped cells which have very thick walls and which contain a few small 

 chloroplasts. A ridged cuticle is present. The stomates are not numerous ; 

 the guard-cells are smaller than the other epidermal cells, and the opening 

 is protected by guard-cell ridges (fig. 8). 



Below the epidermis there is a single layer of large cells which contain 

 numerous chloroplasts and which have thickened cell-walls. The rest of 

 the cortex is a very wide zone consisting of large round cells with very 

 thick walls and with air-spaces between them. These air-spaces are small 

 compared with the size of the cells. These cells contain a large number of 

 starch-grains, which are heaped at the base of the cell. 



There is a well-marked endodermis, consisting of cells with thin suberized 

 walls. The pericycle also is well marked ; it is composed of 2 layers of 

 smaller cells with thickened cell-walls. 



The xylem is composed of wood vessels which form a more or less 

 continuous cylinder, with a few small parenchymatous pith cells in the 

 middle. The phloem forms a continuous band round the xylem and con- 

 tains a fair amount of parenchyma. 



6. Colobanthus quitensis Bartl. 



Growth-form. — " A small densely tufted much-branched plant 1-2 in. 

 high, forming rather soft rounded patches. Leaves variable in size, lower 

 sometimes over \ in. long, upper often very small, ^-^-in., narrow-linear or 

 linear-subulate, acute or mucronate but not acicular at the tip, connate at 

 the base, flat or concave above, convex beneath ; texture soft." 



Anatomy. 



Leaf (fig. 9). — Fig. 9 shows a transverse section of half the leaf. The 

 upper epidermis consists of cells which in transverse section are fairly large 

 and oval. The lateral and the internal walls are thin, but the outer walls 

 are very much thickened. There is no cuticle. The lower epidermis is 

 similar to the upper, except that the cells are slightly smaller and their 

 external walls are not so thick. Stomates are found on both surfaces, but 

 they are more numerous on the upper. The guard-cells are small, have 

 thickened walls, and are raised above the other epidermal cells, but are 

 below their thickened external walls. 



The chlorenchyma is differentiated. The palisade tissue consists of 

 about 3 layers of cells, containing numerous small chloroplasts. The cells 

 are more or less oval in transverse section, and have thin walls ; the inter- 

 cellular air-spaces are small. 



