392 ^ XXIII. LEGUMINOSAE 



regions where the normal rainfall is from 5 to 10 in. In Baluchistan it experi- 

 ences lower temperatures than it does in Sind and the Punjab. In the Indian 

 Peninsula it occurs in regions where the absolute maximum shade temperature 

 varies from 105 to 115 F., the absolute minimum from 40 to 60 F., and the 

 normal rainfall from 20 to 35 in. 



Leaf-shedding, flowering, and fruiting. The foliage becomes some- 

 what thin towards the end of the cold season. The spikes of small yellow 

 flowers appear from March to May, after the new leaves. The pods ripen 

 from June to August ; they are indehiscent, 4-8 in. long, slender, contracted 

 between the seeds, filled with a dry sweetish pulp, and contain 10-15 seeds. 

 The seeds (Fig. 151, a) are 0-2-0-3 in. by 0-15-0-2 in., compressed, ovate 

 oblong or rhomboidal, brown, smooth, hard, with a moderately hard testa. 

 The seed retains its vitality for at least a year. 



Recent experiments in the Montgomery district with seed from coppice- 

 shoots 5-11 years old showed that such seed was sufficiently fertile and that 

 seed from the younger shoots was as fertile as that from the older ones. 

 Ordinarily the seed, if watered, germinates from one to two weeks after sowing. 

 The seed is distributed partly by water, partly by birds, and partly by cattle 

 and other animals, which eat the sweetish pulp of the pods and void the seeds. 



Germination (Fig. 151, b-e). Epigeous. The radicle emerges and the 

 hypocotyl elongated by arching, carrying the cotyledons above ground when it 

 straightens ; as a rule the testa is carried up over the cotyledons, falling with 

 their expansion. 



The seedling (Fig. 151). 



Roots : primary root long, thin, terete, tapering, wiry, yellow turning 

 brown : lateral roots few, short, fibrous, distributed down main root : nodules 

 present. Hypocotyl distinct from root, 0-8-1 -4 in. long, terete, expanded in 

 a ring at the base, white turning green, glabrous, smooth at first, soon becom- 

 ing striate by cracks in the epidermis. Cotyledons very shortly petiolate, 

 0-5 by 0-4 in., elliptical ovate, apex rounded, base sagittate, foliaceous, some- 

 what fleshy, upper surface convex, lower concave, green, glabrous, 5-veined 

 from the base, the two lateral veins very indistinct. Stetn erect at first, soon 

 branching and becoming straggling, zigzag at the nodes, wiry, glabrous, green 

 or reddish, covered with prickles which are at fu\st minute, later 0-1 in. long ; 

 internodes 0-2-0-3 in. long. Leaves alternate. Stipules 0-2 by 0-1 in., falcate, 

 mucronate, green. First leaf pinnate, rachis 0-5 in. long, with occasional^ 

 rudimentary or minute prickles, leaflets usually in five pairs, opposite, with 

 very short petiolules, 0-2 by 0-1 in., obliquely oblong, mucronate, entire. 

 Subsequent leaves bipinnate with one pair of opposite pinnae ; common rachis 

 0-1-0-2 in. long, pinnae 0-3-0-6 in. with 4-6, later 7-8, pairs of leaflets similar 

 to those of first leaf. 



Under ordinary conditions the growth of the seedhng is slow, though by 

 irrigation and weeding more rapid development can be secured. In Sind, 

 even in the case of irrigated sowings, the seedlings normally attain a height of 

 only 6 in. to 1 ft. by the end of the first season. The seedling tends to assume a 

 straggling growth, developing long side branches at the expense of height-growth. 

 It forms a long wiry taproot, which by the end of the second season may 

 attain a length of as much as 2^ ft. or more : this helps it to establish itself 

 in the dry regions in which it grows. Young plants are somewhat sensitive to 

 frost, and small weakly plants are liable to die back to ground-level owing to 



