PALO VERDE. 1 69 



pod, and it will be seen therefore that during the ripening the 

 inner laver or endocarp takes no part in the secondary enlarge- 

 ment of the pod, which accompanies the enlargement of the seeds. 

 This feature distinguishes this species and P. aciilcata from P. 

 Torrcyana. in which latter the whole pod develops without con- 

 stricting between the seeds, and has a form very like that of an 

 ordinary pea pod. 



P. Torrcyana ( Fig. 24), known also as the green-barked acacia, 

 is a larger tree than P. micro pJiylla. with, however, the same gen- 

 eral habit of growth, save that the branches are somewhat less 

 twisted and the terminal twigs longer. This tree grows in 

 " washes,"" and apparently needs more water than its neighbor. 





Fig. 2^. Twig of Palo Verde. (Courtesy of the Popular Science Monthly.) 



It flowers very abundantly, the tree becoming a mass of brilliant 

 yellow when in full bloom. The twigs are usually armed with 

 short thorns, which are very short, leafless branches. The leaflets 

 of this species are considerably larger, and the prominent petal, 

 which in P. microphyl/a is white, is here yellow dotted with 

 red. though slightly difl'erent in form from the rest of the 

 petals. The pod of P. Torrcyana, superficially regarded, diiTers 

 materiall}' from that of the other species, inasmuch, as above 

 pointed out, there is no constriction between the seeds, or at anv 

 rate, very little, and this not constant. The ovary wall is papery, 

 however, and while similar in general appearance to that of the 

 common pea pod, difi'ers from it in the splitting of the outer and 

 inner layers of the wall. In the region of the seed, where the 



