VOL. XVI. NO. 8— BOTANICAL GAZETTE -AUG., 1891. 



A study of some anatomical characters of North American 



(iraminca'. II. 



THEO. HOLM. 



* 



The genus Uniola. 



(WITH PLATES XXI AND XXII.) 



Uniola gracilis Michx., 



/ 



and U. Palmeri V asey . — These four species form together 

 two groups", the first two on the one and the last two on the 

 other side, on account of differences in the anatomical struct- 

 ure of their leaves. It was also to be supposed so, since 

 they inhabit localities so very different. The first group 

 occurs in the woods or swamps, while the second one grows 

 on the sand hills on the sea shore. We shall now see how 

 they differ from each other and from the species described 

 in the preceding part of this paper, U. latifolia, an inhabi- 

 tant of shaded slopes. 



Epidermis. — The epidermis in U. gracilis and U. nitida 

 agrees in most respects with that of U. latifolia, and the 

 only essential difference consists in the presence or absence of 

 long hairs and thorn-shaped expansions ; U. gracilis shows 

 the presence of both organs on the superior face of the blade, 

 but in smaller number than observed in U. latifolia. In U. 

 nitida these organs are entirely wanting. 



The cells of epidermis which cover the sfereome on the 

 inferior face are strongly thickened and laminated in U. 

 gracilis and U. nitida (plate xxil, fig. 6), which shows a dif- 

 ference from what we have seen in U. latifolia. I he bulh- 

 form cells and the stomates show, however, nearly the same 

 -structure and distribution. But in U. paniculata and U. 

 Palmeri the epidermis is entirely different ; the cells on both 

 faces are stronglv thick-walled and porose (plate XXII, fig- 

 IO), rectangular or quadrangular, and arranged so that there 

 is either one short cell between two long ones, as in U. Pal- 

 meri, or even three short between two long ones, as has been 

 observed in U. paniculata. 



Xo hairs are present in these two species, but numerous 

 sharply pointed and porose spines plate XXII, figs. 11-12) 

 proceed from the superior face of the leaf of U. paniculata ( 



