Holm, Some new anatomical characters for certain Gramineae. 113 



Stipa ßlifolia Nees (stony plateaus, Montevideo, Uruguay)» 



„ hyalina Nees (grassy field, Montevideo, Uruguay). 



„ latifolia (Hack.) Arech. (clayey soil, Montevideo» 

 Uruguay). 



„ minor Vas, (Chama, New Mexico). 



„ Keesiana Tr. et Rupr. (grassy fields, Montevideo,. 

 Uruguay). 



„ papposa Nees (dry, clayey soil, Montevideo, Uruguay). 



„ pennata L. var. Neo-Mexicana Thurb. (near Santa Fee,, 

 New Mexico, at an elevation of 5800 ft.). 



„ strida Vas. (Hillsides, Mt. Adams, Washington Terri- 

 tory, at an elevation of 6 — 7000 ft.). 

 The leaves of these species are usually very rigid, but mostly 

 glabrous on the lower face, except in *S'. filiculmis, and the upper 

 face is either scabrous with short papillae (*S', avenacea and S. 

 minor) or provided with long hairs (*S'. capillata, comata, pennata 

 var. neo-mexicana and stricto). The upper surface is more or 

 less deeply furrowed in all the species, enumerated above, with 

 the sole exception of S. ßlifolia, where both faces of the blade 

 are perfectly smooth. The furrowed character of the foliage is 

 constant in these species (excl. S. filifolia), whether the blade be 

 flat or conduplicate, the latter being especially cbaracteristic of 

 S. avenacea, S. ßliculmis and 8. pennata var. neo-mexicana. It 

 may be stated here, that we did not notice the midrib to be 

 more projecting than the other ribs in the leaves with flat blades, 

 while such differentiation was observed in the species with condu- 

 plicate leaves (/S. avenacea, ßliculmis etc.). Bulliform cells occur 

 in all the species, excepting S. ßlifolia, and are located only on 

 the upper face, in the bottom of the furrows. The stomata we 

 have observed to be mostly level with the epidermis and often 

 confined to the upper face of the blade, along the sides of the 

 furrows. 



The mechanical tissue, the stereome, occurs as small groups 

 on either face of the nerves, besides as a larger, isolated group 

 on the leaf- margin; in aS'. capillata, however, this tissue was more 

 amply represented and the cell-walls were heavily thickened to a 

 greater extent than observed in the other species. S. ßlifolia is 

 rather poorly provided with mechanical tissue, as the stereome is 

 here developed only on the leptome-side of the mestome-bundles, 

 but seemed to be absent from the hadrome side. — The mesophyll 

 occurs mostly as a dense, homogeneous tissue of pahsades, and 

 the cells that border on the mestome-bundles radiate towards the 

 Center of these. In a few species, however, the palisades were 

 observed to be relatively short (8. minor and stricta) while the 

 entire mesophyll in S. avenacea, capillata and ßlifolia consisted of 

 roundish cells with no differentiation into palisades. The mestome- 

 bundles are located in the ribs of the blade, and Ä Cliarruana 

 is the only species of the genus examined, in which there are 

 also mestome-bundles in the furrows, beneath the bulliform cells. 

 In all the other species they are confined to the more or less pro- 



