STRUCTURE.] SPIEAL HAIRS. 155 



are among the most beautiful of all microscopical objects, and 

 I can compare them to nothing so well as to stars formed of 

 icicles covered with little glittering points. There is this re- 

 markable in their structure, that each star has a convex centre, 

 whence the rays diverge, appearing to be the apex of a primi- 

 tive hair, of which the rays are the second joints planted 

 perpendicularly upon it. A stellate hair of a similar kind 

 was remarked by the late Mr. Daniel Cooper, in Croton argy- 

 raeum. " The whole cuticle is closely studded with numerous 

 very small stellate hairs (or scales), in the centre of which a 

 small elevated circular orifice (?) is seen, probably in con- 

 nexion with the stomata, and from which, as a centre, the 

 radii proceed, giving the hair or scale a conical appearance, 

 They may indeed be aptly compared, both as to form and 

 apparent structure, to the inverted pappus or seed-down of 

 a compound plant. The numerous brownish spots seen on 

 the under surface of the leaf, are hairs of the same character 

 and structure as those just described, but possessing this dif- 

 ference, viz. that the elevated orifice is of a deep chesnut 

 colour, which tint becomes gradually diffused towards the 

 circumference of the hair, tinging in a slight degree the 

 radii." 



Among the most curious hairs yet discovered are those on 

 the seeds of Acanthodium, which Forskahl says, if mixed with 

 saliva in the palm of the hand dissolve with a crackling 

 noise (cum fragore) . The nature of these hairs has been exa- 

 mined by Mr. Kippist, who has shown that the entire surface 

 of the seed of Acanthodium is covered with whitish hairs, 

 which adhere closely to it in the dry state, being apparently 

 glued together at their extremities. On being placed in water, 

 these hairs are set free, and spread out on all sides ; they are 

 then seen to be bundles of from five to twenty tubular spiral 

 cells, which adhere firmly in their lower portions while their 

 upper parts are free, separating from the common bundle at 

 different heights, and expanding in all directions like plumes, 

 forming a very beautiful microscopical object. The free por- 

 tions of the cells readily unroll, exhibiting the spire formed 

 of one, two, or occasionally three fibres, which may sometimes 

 be seen to branch, and not unfrequently break up into rings. 



