IOWA ACADEMY OP SCIENCES. 151 



it to say here that Duval, Jouve n , Hackel 12 , Gtintz 13 , Samsoe, 

 Liind u and Beal 15 have made valuable contributions. 



Theo. Holm lc has studied Uniola latifolia, U. gracilis, U. nit- 

 ida, U. panicula;a and U. Palmeri, Distichlis, Pleurogogon and 

 Leersia. 



From a study of some of the species of Uniola growing under 

 widely different condition?, he concludes, that of the five spe- 

 cies, the genus show anatomical structures by which they may 

 be easily distinguished. 



He says of the genus Distichlis, that, "Considered altogether, 

 the anatomical structure of the leaf in the genus Distichlis is 

 very uniform, and it does not seem possible to give any 

 special characters by which either of the varieties or the sup- 

 posed species thalasica and prostata may be distinguished from 

 the species maritima; because we have seen that male and 

 female specimens of this last show variations among them- 

 selves nearly equivalent with the differences in the two varie- 

 ties and subspecies." Of Pleuropogon, he says: " Considering 

 now these three species of Pleuropogon together, it is evident 

 that they are, in spite of their great similarity, easily distin- 

 guished from each other" by certain anatomical characters 

 taken from leaf blade. 



THE GENUS SPOROBOLUS. 



The species of the genus Sporobolus are nearly all western or 

 southern. Those occurring in Iowa are characteristic western 

 plants and well adapted to dry climate conditions. The follow- 

 ing species of Sporobolus were studied: Sporobolus heterolepis 

 Gray; S. cryptandrus Gray; S. Hooker i, S. vaginceflorus. 



SPOROBOLUS HETEROLEPIS. 



The epidermal cells (e) are rectangular in shape, with a 

 strongly developed cuticle (c); they vary but little in size. 

 The bullif orm cells (b) occur between each mestome bundle (m), 

 except between the last few at the tip of the leaf, where it is 

 occupied by the streome (st.). The bullif orm cells occur in four 

 or five rows, a large central cell and three or four smaller cells 



11 Histotaxie des feuilles de Graminees. 

 ^Monographia Festucarum Europaearum, 1882. 



13 Untersuchungen ueber die anatomische Structur der Gramineenblaetter, etc. 

 Inaug. Dissert. Leipzig, 1886. 



14 Vejledning til at kjende Graesser i blomterlos Tilstand, Kjobenhavn, 1882. 



15 Grasses of North America for farmers and students 



16 A study of some anatomical characters of X. America Gramineae. Bot. Gazette, 

 Vol. xvi. p. 166, 217, 275. 



