18 



wall is conspicuous. The two uppermost cells of the inner clilorophyll- 

 bearing ring are at least twice as large as the other cells of tlie ring, 

 and are usually wedge-shaped witli the narrow end turned toward the 

 bundle. They are either more liable to lose their contents in cutting or 

 else are less abundantly filled, so that they often resemble colorless 

 parenchyma. iS^o large, thin-walled cells are enclosed by the chloro- 

 phyll ring, but on the other hand large groups of these cells occupy 

 the whole summit of each ridge from one side to the other and from 

 the round chlorophyll cells to the fiber above. The central colorless 

 cells of each ridge are much larger than those that underlie the epider- 

 mis of the sides of the ridge and the fiber at its summit. 



The cells composing the bands of hypodermal fiber show a more 

 uniform character than those of J. pUosa^ though the cells at the sum- 

 mit of the ridges generally show larger cavities than cells of the same 

 tissue elsewhere. Its distribution is the same as in the basal section 

 otJ.pilosa, but the masses of this tissue below the bundles are sepa- 

 rated from the bundle by three or four cells that form a continuous ring 

 with the pitted chloroi)hyll-bearing cells, but are either entirely without 

 contents or have only a few chlorophyll grains. The second ring of 

 chlorophyll-bearing cells is consequently interrupted above the bundle 

 by coh>rless parenchyma and below it by hypodermal fiber, and so exists 

 simply as a baud on each side of the bundle. Besides the cells arranged 

 radially about the bundles, there are others more irregularly lobed that 

 occur near the epidermis where it is contiguous to colorless parenchyma. 

 Median sections do not differ much from basal sections. The ridges are 

 more acute, and two or three secondary bundles intervene between two 

 primary ones. The fibrous cells are a little smaller and have thicker 

 walls, and the cells of the sheaths of the large bundles are more nearly 

 of a uniform size and thickness. Hypodermal fiber does not (as iu 

 J. xnlosa) occur under the colorless parenchyma between ridges. 



DISTICHLIS SPICATA. 



When dry, the leaves of 1). Hincata are involute throughout. The 

 epidermis of the leaf shows irregularities like those of JErar/rostis 

 obtiisijiora, but more numerous and larger, and iu addition covering the 

 fibrous tissue of the lower face. The chlorophyll-bearing parenchyma is 

 not different from that of the other grasses. The bundle sheaths and 

 secondary bundles resemble those of Er(({jrosfi,s ohfusiflora^ but the 

 prinuiry bundles have the plilot'm interspersed witli thick-walled 

 cells like those that separate it Iron i the xylem; these maybe in an 

 irregular group or may form an interrui)ted line dividing the phloi'ui 

 into two i)arts. Colorless parenchyma is absent except in the bands 

 between the bundles. There is none at the summit of the ridges nor 

 within the ring of chlorophyll-bearing cells. The fiber has the same 

 distribution as in Ermjrostis ohtu.sijiora, but all the cells both above 



