Holm, Some new anatomical characteis for certain Gramineae. 107 



leaves of A. spiciformis, and the short ones on those of A. pa- 

 lustris, both which species, as stated abovo, are inhabitants of 

 moist localities in the southern States, And among species from 

 plains and prairies the same Variation exists, some having hairy 

 leaves, and others merelj scabrous, although the species maj 

 grow almost side by side. The bulliform cells show the same 

 location seen in A. fasciculata, but they are not uniformly developed 

 in all the species. They are often verj small, especially in leaves 

 that are deeply furrowed, while they increase in size when the 

 furrows are shallow. They are for instance relatively large in 

 A. Eeverchonis, A. meccana and A. purpurascens, but very small 

 in A. oliganiha and several others. - In some species where the 

 furrows are both deep and narrow, the bulliform cells are seen to 

 be relatively well-developed , for instance in A. 'palustris and 

 A. spiciformis. The colorless tissue is invariably located between 

 the ribs, but shows very little modification in number of layers 

 and rows of cells. 



As to the stereome, which is relatively well represented in 

 Aristida, we find this to be uniformly distributed in tliese species, 

 accompanying the mestome-bundles, and it also occurs underneath 

 the water-storage tissue and on the margins of the blade. It may 

 be very heavily thickened in some species, much less so in others, 

 although from the same localities. In A. spiciformis for example 

 the leaves are well supported in this respect, the stereome being 

 extremely thick-walled and forming large groups of several layers, 

 while the very opposite is to be seen in A. palustris. — The 

 mesophyll, on the other band, appears unvarying in all these 

 species, and we have not noticed a single case in which the cells 

 of this tissue were not differentiated into palisades, showing the 

 same arrangement, as observed in A. fasciculata. — The mestome- 

 bundles show but few modifications, and these as to the relative 

 thickness of the cell-walls ot the inner sheath, which in some 

 species are distinctly thieker than in those of the outer sheath. 

 The crosssection of the mestome-bundles varies from orbicular to 

 oval, both forms being most frequently observed in the same 

 leaf, while it is rare to find the bundles of the orbicular type 

 alone. 



While thus the principal tissues in the leaves of Aristida of 

 this section (Cliaetaria) exhibit a very uniform structure, we noti- 

 ced some deviation as to cell-content of the double parenchyma- 

 sheath, which is not without interest. It is not uncommonly the 

 case that the coloration of the Chlorophyll, contained in these two 

 sheaths, is somewhat different from that of the palisades, it being 

 mostly of a deeper, bluish-green, besides that the Chlorophyll is 

 not always visible as grains in the inner sheath as in the pali- 

 sades and in the outer sheath, but very often it appears as an 

 amorphous cell-content. In A. vagans, ior instance, the color of 

 the Chlorophyll in the inner sheath is deeply bluish-green, while 

 that in the outer is of the same lighter green shade as that in 

 the palisades. In A. meccana the cell-content of both sheaths is 



