SEMEN EICINI. " 5()9 



largo tumid caruncle: from this latter proceeds the raphe as far as the 

 lower end of the ventral surface, where it forks, its point of disappear- 

 ance through the testa being marked by a minute protuberance. If the 

 caruncle is broken off, a black scar, formed of two little depressions, 



remains. 



The shining grey epidermis is beautifully marked with brownish 

 bands and spots, and in this respect exhibits a great variety of colours 

 and markings. It cannot be rubbed off, but may after maceration be 

 peeled off in leathery strips. The black testa, grey within, is not 

 thicker than in croton seed, but is much more brittle. The kernel or 

 nucleus fills the testa completely, and is easily separated, still covered 



by the soft white inner membrane. 



The kernel in respect to structure and situation of the embryo, agrees 

 exactly with that of Croton Tiglium (p. 565), excepting that the some- 

 what gaping cotyledons of Ricinus are proportionately broader, and have 

 their thick midrib provided with 2 or 3 pairs of lateral veins. If not 

 rancid, the kernel has a bland taste, wdth but very slight acridity. 



Microscopic Structure— The thin epidermis consists of pentagonal 

 or hexagonal porous tabular cells, the walls of which are penetrated m 

 certain spots by brownish colouring matter, whence the singular 

 markings on the seed. It is these cells only that become blackened 

 when a thin tano-ential slice is saturated with a solution of feme chloride 



• , , , O 



in alcoliol 



Beneath these tabular cells there is found in the unripe secd^ a rou 



testa. 



ui encrusiea cojouriess ceiis, aepu^ituu m ^ ^^^^^^ — --- 



In the mature seed this layer of cells is not perceptible, and tiiere .. e 

 appears to perish as the seed ripens. The testji itself is built up c^ 



cylindrical, densely packed cells, 300 to 320 ^^k"^- ,\*^"f //t^Jj J; ' 

 mkm. in diameter. The kernel shares the structure ot that of (7. ^l^J^' 

 but is devoid of crystals of oxalate of ca cium If the ^^^^f^^^ 

 of Ricinus is moistened with dilute sulphuric acid, acicular ci}stals ot 

 sulphate of calcium separate from it after a few hours. , , , 



When thin slices of the kernel are examined under c<^^ncenk^^^^^^^^ 

 glycerin, no drops of oil are visible, notwithstanding the almndance ot 

 this latter; and it becomes conspicuous only by addition of much ^ater^ 

 Hence it is probable that the oil exists m the ^f f ;^\^^'"; .^l^; 

 compound with its albuminoid contents.^ As to the latter i^^^^^ 

 form in the albumen of Ricinus beautiful octohedia or tetiahedra, 



which are also found in many other seeds. 



• 1 ^ -.- T1.A most important constituent oi the 



mical Composition— Ine most imp"| -npcled kernels 



seed is the fixed oil, called Castor Oil, of which the peeled kerne 



afford at most half of their weight. 



The oil, if most 

 by pressure without 

 only a very small p 

 the seeds. Hence the seeds themselves, or an emuioxv... ^,^^, 



I' ,,inlU jyroieinarfhier Kvrfcr, Leipzig, 

 ' Gris, Annalcs dcs Sciences Xat., Bot., f„^f j/f ^i tab. 2%. 10; Ffeflfer, Pro- 



I Saclxs, Lehrhuch der Botanllc, 1 874 54. '^fZ^^ftme Botanil; viii. (1872) 429. 

 * For further particulars, seeTrecul, A nn. wmemcaai 

 d(3 Sc. Sat. , Bot. ,x., (1858) 3o5 ; Radikofer, 



464. 



