436 T. Holm — Studies in the Cyperacece. 



Considering the genus Fimbristylis in North America not 

 only "sensu strictiori," but including the species which Torrey 

 referred to Isolepis : stenophylla, ciliatifolia, Warei and 

 eapillaris R. et S., we cannot avoid noticing that the general 

 habit of these plants, both annuals and perennials, is very 

 much the same. A dense cespitose growth is characteristic of 

 most of our species; the leaves are generally narrow with 

 short sheaths, and the flowers are arranged in true spikes, 

 either borne on long peduncles constituting open cymes, or 

 sessile in small heads. While a pubescence is rarely observed 

 in Cyperacece-, it is not uncommon in Fimbristylis, of which 

 several species have the leaves, stems, involucres and scales 

 clothed with short hairs. In examining the inflorescence, the 

 spikes are mostly, as stated above, arranged in open cymes, 

 where the terminal spike is almost sessile and overtopped by 

 the lateral ones. In F. castanea and . /. thermalis several 

 lateral spikes are borne on long peduncles, but with no further 

 ramifications, representing respectively a di- or pleio-chasinm. 

 A similarly constructed cyme is, also, characteristic of F. laxa 

 in plants growing in the vicinity of Brookland, D. C. ; in 

 specimens from Eustis, subtropical Florida, the lateral inflores 

 cences are, on the other hand, decompound, thus agreeing with 

 F. spadicea. The pleiochasium in F. puberula is either simple 

 or decompound ; in the first case the spikes are considerably 

 larger than in the last, where the spikes consequently are more 

 numerous. The most decompound inflorescence is, however, 

 to be found in F. autumnalis, where the secondary branches 

 are pleiochasia, the tertiary, on the contrary, passing over into 

 monochasia of only two spikes, a terminal and a lateral. While 

 in F. eapillaris the inflorescence is typically a pleiochasium, it 

 is not unusual to meet with specimens where the flowers are 

 reduced to a single spike, at the base of which a long involucral 

 bract is often noticeable, but without supporting any lateral 

 branch. Similar empty involucral leaves, but reduced to scale- 

 like, long-pointed bracts, occur also at the bases of several of 

 the spikes, indicating the place of non-developed inflorescential 

 branches. In species with sessile spikes, F. Warei and F. 

 stenophylla, the composition of the inflorescence becomes 

 more indistinct, since all the peduncles are very short and the 

 characteristic clado-prophyllon entirely suppressed, a fact that 

 is known also from other genera of Cyperacece with similarly 

 aggregated spikes : species of Cyperus, Dichromena, Scirpus, 

 Carex and others. But where a clado-prophyllon is developed, 

 this is readily noticed at the very base of each lateral peduncle 

 as a tubular sheath, more or less puberulent in our species of 

 Fimbristylis. It varies somewhat in shape, being compressed 

 in F. autumnalis and its more southern ally F. complanata, 



