safford: myrmecophilous acacias 365 



18. Acacia Hindsii Benth. Lond. Joum. Bot. 1: 504. 1842. 



Tj'pe in the Kew Herbarium, collected on the shore of ManzanilJo 

 Bay, State of Colima, Mexico, 1836-39, by Dr. Richard B. Hinds, Sur- 

 geon of H. M. S. Sidphw (no. 248). 



19. Acacia bursaria Schenck, Repert. Nov. Sp. Fedde 12: 363. 1913. 

 —Bot. Jahrb. Engler 50: 485. 1914. 



Tj'pe in the Berlin Herbarium, collected near San Felipe, Guatemala, 

 February, 1878, by I^emouilli and Carlo (no. 1129). 



20. Acacia sinaloensis sp. nov. Closely related to A. Hindsii Benth. 

 and .4. bursaria Schenck, but distinguished by its lighter-colored, broadly 

 V-shaped or Y-shaped spines, these alternate, regularly disposed at 

 intervals of 3 or 4 cm. along the slender, straight, terete, glabrous, reddish 

 bro^^^l branches; length of spines 30 to 40 mm., breadth along the suture 

 formed by the connate flattened bases 12 to 14 mm.; extremities terete, 

 tapering into a very sharp point; color of spines usually olivaceous or 

 yellowish green, turning bro"\Aaiish or buff-colored when old and dead. 

 Vegetative leaves fernlike, elliptical or oblong in outline; main rachis 

 grooved above, sparsely pubescent (under the microscope), bearing a 

 raised porelike gland at the base of each pair of pinnae; base of the 

 rachis (petiole) with 1 to 3 similar glands; pirniae 12 to 18 pairs, linear, 

 approximate, their rachises 30 to 34 mm. long, sparsely pubescent; 

 leaflets 5.2 mm. long, 1.4 mm. broad, thin and membranaceous when 

 3'oung, at length subcoriaceous, manj- of them bearing caducous amber- 

 colored apical bodies, those without the latter acuminate at the apex, 

 the margins of the leaflets bearing very short fine hairs (under the 

 microscope) from the base to the apex, the base very obhque, the midrib 

 conspicuous beneath, the lateral nerves scarcely visible even with the 

 microscope. Leaves of the small axillary branchlets smaller, with fewer 

 pairs of pinnae, these composed of fewer, relatively broader, more rounded 

 leaflets, their rachises provided at the base with a pair of subulate 

 stipular spines, usually without a basal nectar gland, but with one of these 

 at the base of each pair of pimiae. Flowers wanting, but apparently 

 borne in a lax spike. Fruit a falcate or retrocurved follicle dehiscing 

 along the ventral suture, 11 mm. broad near the middle, acuminate at the 

 apex, tapering at the base; seeds 8 to 10, in a single row, embedded in a 

 yellowish white, thin aril, crowded and compressed, oblong or clavate, 

 8 or 9 mm. long, 4 mm. broad, 2 mm. thick, tapering toward the base into 

 a rounded point, the testa dark brown, hard and polished, with an 

 oblanceolate area enclosed by a raised line on each side. 



Type in the U. S. National Herbarium, no. 636818, collected in the 

 vicinity of Villa Union, State of Sinaloa, Mexico, growing about a pond, 

 April 2, 1910, by Rose, Standley, and Russell (no. 13972). 



Section 8. Leiocerates 



Large stipular spines of vegetative branches resembling polished 

 subterete spreading honis, somewhat compressed at the connate bases. 

 Smaller spines of the very short axillary branchlets subulate. Leaf 



