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48 BOTANY OF THE DEATH VALLEY EXPEDITION. 



The leaves are variable in size, form, and area of surface, often reaching a length of 

 5 cm. and a width of 1 era. They are green in color, and are provided scantily in 

 varied proportions with two kinds of hairs — one long, curled, and several-celled ; the 

 other short, made up of two or three columns of cells, and surmounted by a thick, 

 spherical gland. Each column contains from one to three short cells, placed end to 

 end. In the axils of many of the leaves are buds, evidently prepared for develop- 

 ment during the following year, which are densely woolly with the hairs of the 

 fcind lirst described. 



Atriplex confertifoUa — The wood and bark are similar to those of Amphiachyris, 

 The leaves have an area., on either surface, of 0.5 to 1 sq. cm. The netted, partly anas- 

 '•tomosing veins of the leaf are densely coated with cells full of chlorophyll, while the 

 'cells of the intervening spaces contain very little. Stomata are abundant on both 

 surfaces of the leaf, and a thick coating of large, thin-walled, bladdery cells closely 

 ■covers and protects the epidermis. Atriplex canescens, A. hymen elytra, and A. 

 .polycarpa are all characterized by leaves of large surface-area and similar modi- 

 •ficatifins. 



liebbia juncea aspera. — The stem wood is soft, with the annual rings indistin- 

 'gftishable and the pith large. The thick, filiform-linear leaves are scabrous with 

 Oppressed, short, stiff-pointed hairs. 



BigeJovia teretifolia — The wood is hard and of slow growth, but the rings difficult 

 •to distinguish; while the bark is like that of Amphiachyris. The leaves are nar- 

 "rowly linear, thick, and semiterete. They have no pubescence, but are covered 

 ''with pits, at the bottom of each of which is a rcsiu-gland. Three resin-passages 

 run longitudinally through the leaf. 



Cassia armata.— The stem is green, striate, apparently glabrous, and evidently 

 performs for several years the function of transpiration. The wood is thin, the 

 pith large, and the annual rings indistinguishable. The epidermis of the stem is 

 covered by a dense coating of short, thiok, unicellular, club-shaped hairs, each 

 of which is reflexod and appressed to the stem. This hairy coating resembles in 

 miniature a roof covered with cylindrical tiles. Occasionally one of the hairs is 

 conspicuously larger than the others and possesses the rcmarkablo character of 

 containing chlorophyll. Stomata are present in the epidermis. The rachis of the 

 compound leaf is about 5 cm. long, and reaches a thickness of 2 mm. and a breadth 

 of 2.5 mm. In transection the rachis is seen to be made up of chlorophylless, pith- 

 like tissue, bearing on its outer surface, beneath the epidermis, a thin layer of 

 chlorophyllose cells. The rachis bears a few pairs of small, deciduous leaflets, which, 

 like the rachis itself, are glabrous or bear a very few appressed, sbort, cylindrical 

 hairs. 



Cercits engelmanni. — This is similar in its structure to Echinocactus polycephahis, but - 

 the stem is cylindrical instead of globular, and bears no wooUy hairs at its apex. 



Dalca fiemontU.—Tho leaflets are generally oblong in outline, 5 to 10 mm. long, 

 thick, and moderately pubescent, with appressed silky hairs, which, while the leaflets 

 are young, form a dense covering over them. Imbedded in the substance of the leaf 

 are scattered resin-glands. The leaflets appear to be early deciduous. 



Dalca polyadenia.— The stems are of slow growth, and very little thickening takes 

 place in the bark. The epidermis of the stem is densely covered with a coating of 

 retrorsoly appressed, short, straight hairs, among which are interspersed large, ses- 

 sile resin-glands. The deciduous compound leaves are covered, but less densely, 

 with similar hairs and glands. 



Echinocactus polyaneistrits is modified in a manner similar to E. polycephalus, except 

 that the stems grow singly and bear no woolly hairs at their apices. 



Echinocactus polycephalus. — This cactus grows in sessile groups made up of a few 

 globular, ribbed, chlorophyllose stems without foliage. The thick epidermis is 

 glabrous and the interior of the stem very mucilaginous. The growing, depressed 

 apex of the stem is covered with a mass of long, white, implexed woolly hairs, which 

 drop away as the parts become older. 



