RADIX RHEI. 491 



grains. Their colour is a light pinkish grey with an elongated brown 

 spot on the vaulted back, due to the embryo, which at this point is in 

 c ose contact with the translucent testa. From this brown spot the 

 thick radicle runs to the top of the seed. The hollow side of the seed 

 is also brown and partially covered with a thin white membrane. 



The seeds are highly mucilaginous in the mouth, but have neither 

 taste nor odour. Those of the allied P, Psyllhim have nearly the same 

 form, but are shining and of a dark browm hue. 



Mic 



■oscopic Structure — This can be best investigated by immers- 

 ing the seed in benzol, as in this medium the mucilage is insoluble. 

 When thus examined, the whole surface is seen to consist of polyhedral 

 cells, separated by a very thin brown layer from the albumen, which on 



the back of the seed is only 70 mkm. thick. The albumen is made up 

 of thick-walled cells, loaded with granules of matter which acquire an 

 orange hue on addition of iodine. ' The two cotyledons adhere in a direc- 

 tion perpendicular to the bottom of the furrow ; tlieir tissue is comppscl 

 of thin-Avalled smaller cells, containing also albuminous granules and 

 drops of fatty oil. 



If the seed is immersed in w^ater, the cells composing the epidermis 

 instantly swell and elongate, and soon burst, leaving only fragments of 



their walls. When examined under olycerin, the change is more gradual, 



formed of the secondary deposits on their walls, as in linseed and 



(lumce pips. 



Chemical Composition— Mucilage is so abundantly yielded by 

 these seeds, that one part of them with 20 parts of water forms a, tlnck 

 tasteless jelly. On addition of a larger quantity of water and filtering, 

 hut little mucilage passes, the greater part of it adhering to the seeds. 

 The mucilage separated by straining with pressure does not redden 

 litmus, is not affected by iodine, nor precipitated by borax, alcohol or 

 ferric chloride. The fat oil and albuminous matter of the seed have 

 not been examined. 



Uses-A decoction of the seeds (1 p. to 70 p- of water) is employe.! 

 in India as a cooling, demulcent drink'. The seeds powdered and mixed 

 with sugar, or made gelatinous with water, are sometimes given m 



chronic diarrhoea. 



POLYGONACE^. 



RADIX RHEI. 



Ithiiharh; F. Jlhaharbe; G. Ilhabarhcr 



