FIELD COLUMBIAN MUSEUM BOTANY, VOL. III. 



internerves puberulent, subtending a brown, scabrous palea nearly 

 its own length; fruiting glumes 1.7x5.7 mm., lanceolate-ovate, short- 

 acuminate, glume 5-nerved, the basal keels winged; palea puberulent 

 above between the two nerves. Grain stramineous, oval-oblong, 

 apiculate, 1.7x2.8 mm., in section convexo-concave. 



Hab. Merida, Aug. 27, 1865, Schott 498 in part; "Very abund- 

 ant on cultivated lands near Izamal, 18 inches high," Gaunter 1084; 

 arid rock-strewn plain south of Progreso, Millspaugh PL Utowana 

 1698, Chichankanab Gaunter 2448. 



Cenchrus insularis Scribn. Field Col. Mus. Bot. 2:26. 



Spikes exserted, 5-7 cm. long, of 8-16 involucres, i?xi6 mm. 

 including bristles, on densely hirsute pedicels, the 78 divisions 

 spine-pointed, erect; 

 spines 6-9 mm. long, 

 purplish, pubescent, 

 long - ciliate at the 

 base, retrorsely 

 barbed toward the 

 apex; basal bristles 

 numerous, slender, 

 glabrous. Spikelets 

 2-3 in each invol- 

 ucre, 2.2x6.5 mm., 

 o ; vate-l anceolate, 

 acurriinate, glabrous. 

 First glume */ 2 the 

 length of the second, 

 lanceolate, i-nerved, 

 hyaline, usually 

 wanting; second ^ 

 the length of the 

 spikelet, ovate, trun- 

 cate, more or less toothed by the excurrent tips of the nerves, 5-nerved; 

 third nearly the length of the floral glume, 5-nerved, acute, subtend- 

 ing a puberulent palea nearly its own length with 2 retrorsely his- 

 pid nerves; fruiting glumes, 2.1x6.5 mm., ovate-lanceolate, falcate- 

 acuminate; floral glume 5-nerved, scabrous toward the apex, palea 

 puberulent above between the 2 faint nerves. Grain stramineous, 

 obovoid-oblong, apiculate, 1.7x2.8 mm.; in section convexo-concave. 



Hab. Pajaros Island, Alacran Shoal, March 8, 1899, Millspaugh 

 PL Utowana /75p. (Type in Field Col. Mus. Herb. No. 61759.) 

 One plant only found, though being in full fruit others may appear 

 from seed. This plant grew in the very center of the island where 

 the booby nests are the thickest, and was the only representative of 

 the species on the shoals. No. 1607 reported in Field Col. Mus. Bot. 

 2:2*7 is C. tribuloides, not this species, which has only been found on 

 the Alacrans. 



Cenchrus tribuloides L. Sp. PI. 1050. 



Spikes included at base or short-exserted, 3-6 cm. long, of 10-16 



