192 LEGUMINOS^. 



and hyoscyamine, were further examined by many other experimenters 

 on mammals or birds. The action of the poison when taken internally 

 was found rapidly to affect the cardiac contractions and finally to 

 paralyze the heart. 



Description — The fruit of Physostigma is a dehiscent, oblong- 

 legume about 7 inches in length, containing 2 or 3 seeds. The latter, 

 commonly known as Calabar Beans, are 1 to If inches long, about f 

 of an inch broad, and f to f of an inch in thickness, weighing on an 

 average twenty seeds, 67 grains each. 



They have an oblong, subreniform outline, one side being straight 

 or but slightly incurved, the other boldly arched. The latter is marked 

 by a broad furrow, ^ of an inch wide, bordered with raised edges, and 

 running from the micropyle, which is a small funnel-shaped depression, 

 quite round the opposite end of the seed. In the middle of this 

 remarkable furrow the raphe is seen as a long raised suture running 

 from end to end. The surface of the seed is somewhat rough, but has 

 a dull polish ; it is of a deep chocolate brown, passing into a lighter 

 tint on the ridges bordering the furrow. The latter is black, dull, and 

 finely rugose. 



When the seed is broken the cotyledons are found adherent to the 

 testa, with a large cavity between them. The air thus included causes 

 the seeds to float on water, but they sink immediately when 

 broken. After digestion for some hours in warm water, the testa 

 haviag been previously cracked, the whole seed softens and swells so 

 that its structure may be easily studied. Each cotyledon is then seen 

 to be marked on the hilum - side by a long 'shallow furrow, at 

 one end of which, just below the micropyle, lies the plumule and 

 radicle. A dark brown inner membrane, constituting part of the testa, 

 surrounds the cotyledons. 



The seeds have scarcely any taste, or not more than an ordinary 

 bean; nor in the dry state have they any odour. After being boiled, 

 or when their alcoholic tincture is evaporated, an odour suggesting 

 cantharides is developed. 



Microscopic Structure — The cotyledons are built up of large 

 globular or ovoid cells, those of the outermost layer being smaller and 

 of rather cubic form. This parenchyme is loaded with starch granules, 

 frequently as much as 50 mkm. in diameter. Their interior part is less 

 distinctly stratified than the outer; the hollow centre radiates in 

 various directions around the axis of the ovate granule. Polarized 

 light does not show a cross as in other more globular starch granules, 

 but two elliptic curves approaching one another near the axis of the 

 granule. Similar starch granules are commonly met with in the seeds 

 of LeguminoscB. 



In the Calabar seeds the starch is accompanied by numerous par- 

 ticles of albuminous matter becoming distinctly perceptible by addition 

 of iodine, which imparts to them an orange colouration. 



The shell of the seed is built up of four different layers ; the pre- 

 vailing layer consists of very long, simply cylindrical cells, densely 

 packed so as to form only one radial row. Tison^has endeavoured 

 to ascertain in what region of the seed the active principle 



* Hisioire de la Five de Calabar, Paris, 1 873. 38. 



