Vol. XVI. No. 10— Botanical Gazette — Oct., 1891. 



A study of some anatomical characters of North Ameri- 

 can Grainineie. III. 



THEO. HOLM. 



Distichlis and Pleuropogon. 



(WITH PLATES XXIII AND XXIV.) 



DistickHs mwitimi Rafinesque.— While engaged in study- 

 ing the leaf-structure of Uniola Palmeri Vasey, I was well 

 aware of the great similarity that exists between this species 

 and the genus Distichlis in external characters of the in- 

 florescence, the rhizome, and the rigid, densely 2-ranked, in- 

 volute leaves. Now having examined the anatomy of the 

 leaf of a number of specimens of Distichlis, the similarity 

 between these two plants has been found to be so striking 

 that it seems most natural to consider Uniola Palmeri as a true 

 Distichlis. Professor F. Lamson-Scribner has also informed 

 me that on seeing the plant, he immediately took it for a Dis- 

 tichlis and was unable to distinguish it from this genus. 



In studying the leaf-structure of Distichlis maritima, several 

 male and 'female individuals have been examined from differ- 

 ent parts of North America, and although the structure is 

 essentially the same, a few differences have been observed. 

 If we take the entire structure of the leaf into consideration 

 and compare it with that of the so-called Uniola Pa,m ^ n ' 

 described in the preceding paper, it will be difficult to find 

 any essential difference. We may take for comparison the 

 leaf of a female plant of D. maritima from western Texas 

 of which a transverse section is figured on plate XX HI, fig. I. 



The epidermis of both faces shows the same structure as 

 described for the superior face of Uniola Palmeri, having 

 numerous warts and rather pointed epidermal expansions. 

 The structure of the mestome-bundles is exactly the same 

 and the development of these as well as their distribution 

 accords perfectly with what we have seen in U. Palmeri, viz.. 

 a thin-walled and green proper parenchyma-sheath, surround- 

 ing, at least in the largest bundles, a closed ring of very tn.ck- 

 walled parenchyma. Furthermore the leptome and hadrome 

 are often separated by a layer of similar parenchyma, and 



