242 



PLANT ORGANS OR PARTS OF PLANTS. 



which is closely similar to Mucuna cylindrosperma, 

 Welwitsch.* 



The seeds, two or three in number, are contained in 

 pods about i8 cm. long. 



Description. — Calabar beans are chocolate-colored and 



Fig. 69. — Physostigma. 

 Cross-section of outer portion of physostigma seed: p, Palisade 

 cells; t (macrosclereids), sclereids of spongy portion ; s, pigment layer; 

 /, microsclereids ; a, outer seed coat with small vessels; i, inner seed 

 coat; c, cotyledon (Tschirch). 



2.5 cm. long, 2 cm. broad and 1.5 cm. thick. In 



shape they are oblong-reniform, one side being flat 



or slightly convex and the other well curved. Along 



* Holmes: Ph. Jour., ix, 1879, 913. 



