HITCHCOCK AND CHASE GRASSES OF THE WEST INDIES. 397 



107. ARTHROSTYLIDIUM Rupr. 1 



Spikelets few-flowered, in racemes, the lower 1 or 2 lemmas empty, the 

 rachilla articulate between the florets (rarely below the glumes). In Cuba the 

 species are called " tibisi " as are those of Lasiacis. 2 



Blades subcapillary, 1 to 3 mm. wide, as much as 30 cm. long, drying involute. 



1. A. capillifolium. 

 Blades not subcapillary, flat. 



Tips of culms and branches retrorse-scabrous. 



Blades about 6 mm. wide-!. 8. A. haitiense. 



Blades 10 to 12 mm. wide 9. A. multispicatum. 



Tips of culms and branches not retrorse-scabrous. 



Blades not over 5 cm. long, usually shorter (rarely 6 cm. long in young 

 shoots ) . 



Sheaths not bristly ; inflorescence racemose 2. A. sarmentosum. 



Sheaths conspicuously squarrose-bristly at the summit; inflo- 

 rescence elongate, consisting of distant groups of spikelets. 



3. A. distichum. 

 Blades or some of them at least 8 cm. long; inflorescence racemose. 

 Sheaths not bristly at the summit, or with but one or two weak 

 bristles. 

 Blades pubescent beneath, thick, rigid, the midnerve and mar-^^/J^^^ 



gins prominent 6. A. urbanii. 4^<^£&j 



Blades glabrous. 



Spikelets crowded, terminating the densely whorled leafy 



branches ; blades acuminate 5. A. prestoei. 



Spikelets not crowded, borne on solitary or fascicled axil- 

 lary branchlets ; blades obtuse at tip. 



13. A. obtusatum. 

 Sheaths bristly at the summit. 



Bristles 1 to 2 cm. long, some of them squarrose or reflexed, not 



curled and tangled at the tips 4. A. fimbriatum. 



Bristles less than 5 mm. long, erect, the tips curled and 

 tangled. 



Blades pubescent beneath 7. A. pubescens. 



Blades glabrous. k Wvk-*^^ 



Spikelets divergent on a zigzag axis, the flowering 



branches axillary 10. A. excelsum. 



Spikelets erect or appressed, the axis not zigzag. 



Inflorescence of slender racemes, leafless or nearly 



so 11. A. cubense. 



Inflorescence of narrow panicles, terminating leafy 

 branches 12. A. angustifolium. 



1. Arthrostylidium capillifolium Griseb. Mem. Amer. Acad. n. ser. 8: 531. 1862. 

 Arundinaria capillifolia Hack. Oesterr. Bot. Zeitschr. 53: 69. 1903. 



1 In the tribe Bamboseae the genera are here accepted as distinguished by 

 Hackel (Engl. & Prantl, Pflanzenfam. 2 2 : 1887). Further field study and col- 

 lections of flowering plants are necessary before the true generic characters of 

 this tribe can be understood. 



2 In this and other genera of bamboos the description of habit is necessarily 

 omitted in those species not observed by the authors and not adequately 

 described from living plants. 



