56 TEANSACTIOXS AND PROCEEDINGS OF THE [Sess lviii 



alkaloid, which he has named Vinalin. The most 

 interesting feature of the Viiml, however, is its spines. 

 Other species of the genus Prosopis are commonly 

 provided with spines, but in Prosopis ruscifolia these attain 

 to gigantic dimensions, so that a tiny twig an eighth of 

 an inch thick may bear spines half-an-inch thick at the 

 thickest point, and 5 inches in length. These spines 

 would form an interesting problem to those who hold the 

 opinion that spines are merely starved branches, and that 

 they mark loss of vegetative power, for here we have the 

 spines enormously larger than the parent branch from 

 which they are given forth. 



The presence and the use of these enormous spines is, 

 however, in any case very puzzling. The ordinary function 

 of spines is as a protection against herbivorous animals, 

 but the Vinal is a large tree, and there are no large 

 indigenous herbivora, except deer and tapirs, both of which 

 are obviously unable to prey upon the foliage. It seems 

 to me most reasonable to look upon the Viiml as a survival 

 of what was fittest a long period of time since, when, as 

 in tertiary and post-tertiary times, the region which it 

 inhabits had a population of large herbivorous mammals. 



Desmanthcs vihgatus, Willd. 



Hab. — Fortin Page. In the open palmar ; growing a 

 few plants together, often on termite hills. 



Mimosa aspekata, L. 



Hab. — Eio I'arana near Goya. Fl. Jan. 



Mimosa cixerea. Veil. 



Hab. — Open palmar near Fortin Page. 



Mimosa steigillosa, Torr. et Gr. 



Hab. — Fortin Page. Common in the open palmar, 

 resembling clover in its general habit. Fl. 20th Oct. 



Mimosa sp. I — Specimen too imperfect for deter- 

 mination. 



Acacia boxariensis, GilL 



Hab. — Lower Pilcomayo, by the river margin. 



