1891.] Anatomical Characters of. N. Am. Graminece. * 223 



sue of parenchyma. U. Palmeri has not these last mentioned 

 stereome-groups opposite the bulliform cells, but merely one 

 above and one below each mestome-bundle, both of them bor- 

 dering on the parenchyma-sheath. 



Besides these groups of stereome, there is also one large 

 group on each of the two margins of the blade of both 17. 

 paniculata and U. Palmeri. 



The mcsophylL — This tissue is most extensive in U. gra- 

 cilis and U. nitida, where it forms broad layers of rather large 

 cells between the mestome-bundles and is in contact with 

 epidermis on both faces. It is relatively but sparingly repre- 

 sented in the two other species, and is here not only separated 

 by the mestome-bundles with their corresponding groups of 

 stereome, but also by the broad layers of uncolored paren- 

 chyma. Thus there is one two isolated group of mesophyll on 

 each side of the mestome-bundles. The cells of this tissue 

 are, in U. paniculata and U. Palmeri, rectangular, very narrow 

 and thin-walled. 



The uncolored parenchyma. — This is very distinct in the 

 carene of U. gracilis (plate XXI, fig. 2), where it occupies a 

 large space between the mestome-bundle and the superior 

 epidermis. There is also in this same species a single stra- 

 tum of uncolored cells outside the parenchyma-sheath of the 

 two mestome-bundles next to the midrib and bordering on 

 the carene (plate XXI, fig. 1). This parenchyma is also pres- 

 ent and relatively much more abundant in U. paniculata and 

 U. Palmeri, where it forms large groups between the bulliform 

 cells and the epidermis of the inferior face. 



From the foregoing it will be seen that these five species 

 of the genus Uniola show several anatomical characters in 

 their leaf-structure by which they may easily be distinguished. 

 These characters may be summarized as follows: 



Epidermis. 



T j U. paniculata. 



^arge cells in alternation with small ones - -j tj p a lmeri 



r ( U. Iatifolia. 



A-ong hairs on the superior face ) tj. gracilis 



1 U. iatifolia. 



Thorn shaped expansions on the superior face \ u gracilis. 



r r / U. paniculata. 



Wart-shaped expansions on the superior face U. Palmeri. 



i U Iatifolia 

 Bulliform cells forming large groups 1 lJ - W™*N* 



* 



