T. Holm — Studies in the Cyperacew. 437 



or bicarinate in F. castanea and F. spadicea, or it is cyliudric 

 as in the other species ; the apex is prolonged into two subu- 

 late teeth in F. laxa and F. castanea, but merely slightly 

 oblique in the others. While the inflorescence of Flmbristylis 

 does not show any remarkable deviation from that of other 

 Cyperacew, we have observed in the disposition of the leaves 

 a very peculiar exception from the ordinary rule in this order, 

 at least in some species. As invariably quoted in botanical 

 manuals, the tristichous leaf -arrangement is the characteristic 

 one of the Cyperacew, while on the contrary the distichous 

 that of the Graminew. It would hardly be natural to suppose 

 that any such rule should be stable for either of these orders, 

 since exceptions are known if not from the leaves then at least 

 from the arrangement of the spikelets and the inflorescential 

 branches. We might merely call attention to the panicles of a 

 number of Graminew, of which the branches are not distich- 

 ous ; besides that the spikelets are sometimes spirally arranged, 

 . as for instance in species of Eragrostis. In the Cyperacew 

 the distichous arrangement of the flowers with their bracts is 

 well known as the very characteristic of Cyperus, Didichium, 

 partly also of Scleria and Dichromena. But the arrangement 

 of the stem-leaves has, so far, usually been described as tris- 

 tichous in the Cyperacew, in spite of the fact that Kunth, in 

 his diagnosis of F. autumnalis, characterized the leaves as 

 " distichis," a statement which is absolutely correct. The 

 leaves of this species have laterally compressed sheaths, which 

 soon become split, and the blades are furthermore held in a 

 very peculiar position: with the one margin turned towards, 

 the axis or the flower-bearing stem. Although the leaf-blades 

 are not isolateral, they invariably show this position, a fact that 

 we have never noticed before in any of our American species 

 with corresponding anatomical structure excepting in F. com- 

 planata. The distichous arrangement of the leaves is, how- 

 ever, also to be seen in F. castanea and F. spadicea, but the 

 leaf-blades are not turned to the side in these species ; they 

 occupy the usual position as dorsi ventral leaves. Considered 

 from a morphological view-point, it seems strange that such 

 disposition of leaves should be found in a genus like Fimbris- 

 tylis, in which all the other foliar organs, involucral-leaves and 

 floral bracts are arranged in spirals ; it would seem more natu- 

 ral to a genus like Cyperus or Didichium with the distichous 

 flowers. And by examining the internal structure of such 

 leaves, it seems still more surprising that we find a number of 

 analogies rather than important variations. Furthermore when 

 we compare our North American species with each other, it 

 will be seen from the following pages, that even if they inhabit 

 localities differing greatly in climate and soil, their internal 



