268 BOTANICAL GAZETTE [October 



Euphorbia polygonifolia. — A little prostrate succulent annual 

 with abundant latex. Leaves small, thick, inclined to be folded 

 at right angles on the midrib; walls of epidermis thickened, outer 

 9-12 ^ on the upper surface and 15 p at the edges of the leaf; 

 stomata sunken to the depth of the epidermis; a layer of palisade 

 cells next the upper epidermis and "festoon" palisade about the 

 bundles; a layer of water-storage tissue next the lower epidermis; 

 cells at the bend of the midrib collenchymatous; small develop- 

 ment of vascular elements. Stem woody for so small a plant, 

 having a compact vascular cylinder; walls of epidermis thick, 

 outer 8 /*, cuticle 4.6 /*; cells below thickened; latex tubes con- 

 spicuous. 



Corispermum hyssopifolium. — Low, branching, succulent annual. 

 Leaf thick, narrow, linear; two layers of palisade on both sides 

 and water-storage tissue in the center; walls of the epidermis 

 thickened, outer 16 /*; cells with thickened walls about the midrib 

 at the edges of the leaf. Stem with two la 



ma 



walls of epidermis 



heavy, outer 9.6/*. Root sclerenchymatous except a few outer 

 layers. 



Artemisia caudata and A. canadensis. — Stout, bushy biennials 

 or perennials. Leaf- divided, divisions thick, smallest almost 

 cylindrical, generally pubescent; double row of palisade on both 

 surfaces, water-storage tissue inside; walls of epidermis thickened, 

 outer wall 6-1 1 /*; stomata sunken one-half the depth of the 

 epidermal cells. Stem with pith rapidly reduced after the first 



almost 



masses 



matous; considerable cork. 



Cirsium Pikheri. — Biennial, tomentose. Leaf very thick, with 

 revolute margins; epidermal cells small, with thickened walls, 

 outer 6.4 /*; chlorophyll confined to 2-4 outer layers of cells; the 

 rest water-storage tissue with cells increasing in size toward the 

 center with large air spaces between. Stem generally hollow, 



masses 



fibers; rays wider than the bundles, the cells with thickened 

 outer cells of cortex collenchymatous. 



j 



