T. Holm — Studies in the Cyperacew. 301 



Art. XXXV. — Studies in the Cyperacew ; by Theo. Holm. 

 XXIII. The Inflorescence of Cyperus in North America. 

 (With figures in the text.) 



A general consideration of the structure of the inflorescence 

 in Cyperus must necessarily result in the conclusion, that 

 throughout the genus the structure is most essentially the same. 

 The components are invariably the same: the in volucral leaves, 

 the prophylla, the branches, the floral bracts and the flowers, 

 all these are clearly represented in each species; nevertheless 

 some differences in aspect are frequently quite obvious, but 

 depend to a very large extent simply upon mere variations in 

 the length of the inflorescential branches, in the position of 

 the spikes, their external shape and the manifold structure of 

 the small, floral bracts. — Some of these characters, however, 

 are often deceptive; because in the same species, it is not 

 unusual to meet with individuals in which the number of spikes 

 is reduced to one or two, nearly sessile, with the involucral 

 leaves and prophylla very inconspicuous, while typically 

 developed specimens may possess an ample inflorescence with 

 long leaves and tubular prophylla. 



The division of the genus in sections : Pycreus, Cyperus 

 proper, Papyrus, Diclidium and Mariscus, is not directly based 

 upon deviation in respect to the real components of the inflores- 

 cence, but only in regard to the structure of the spikes and the 

 flowers, especially the arrangement and direction of the spikes, 

 the shape of the rhachis and the structure of the achenes. The 

 specific distinction is not materially dependent upon the main 

 inflorescence, inasmuch as the same form is to be observed in 

 remote sections of the genus, but here our attention is directed 

 to the color and minor structure of the spikes, which constitute 

 the ultimate divisions of the inflorescence, also, in some cases, 

 to the structure of the rhizome. 



In presenting a brief description of the inflorescence of the 

 genus, we freely admit that we have nothing to add to the old, 

 but most excellent one, given by Fenzl in his paper on 

 Cyperus Jaquini Schrad,* or to the more recent one by 

 Clarke,! but we wish to bring out a few points relating to the 

 structure and function of the fore -leaves, which deserve some 

 attention and which ought not to be passed by entirely in 

 systematic treatments of the genus, as has been the case in 

 American literature. It is, furthermore, the writer's desire 

 to demonstrate, that some of the foliar organs which are pres- 



*Denkschr. Math.-Naturw. CI. Akad. d. Wiss., Wien, vol. 8, 1855. 

 f Journ. Linn. Soc, vol. 21. 



