242 SENECIO VULGARIS. 



scope in a particular direction, the sky seemed to swarm with pale, 

 glittering, falling bodies, like a miniature shower of meteors, and 

 he came to the conclusion that they were the plumed seeds of one 

 of the Composite plants, probably those of the thistle, glancing in 

 the sun-beams. 



The hairs of the corona, or " plume " of the common Ground- 

 sel are very transparent, and are composed of oblong and tolerably 

 regular cells, apparently filled with air. They are very thorn-like, 

 and have longitudinal markings upon them, which are probably 

 grooves (Plate 26, Fig. 2). 



The oblong, cylindrical seed-vessel, called in botanical lan- 

 guage the AchcBnium, is, when mature, of a rich brown colour, and 

 has several rows of minute silvery hairs upon its surface. The 

 upper portion is formed into a ring-hke tissue, from which the 

 corona of hairs springs. In the drawing, Plate 26, Fig. i, I have 

 purposely left one-half of this ring destitute of plumes, that the 

 appearance may be better understood. 



In regard to the short silvery hairs of the achsenia, the Micro- 

 graphic Dictionary refers to their interesting character, in that when 

 brought into contact with water they emit spiral fibres. In the 

 A7inals of Natural History for 1841, the same character is referred 

 to. The seeds should be quite mature, and must be gathered 

 before dew or rain has visited them. I have witnessed this curious 

 process in seeds which have been matured under home protection, 

 and the drawing. Fig. 3, is made from a camera-lucida drawing 

 immediately after the bursting-forth of the spiral fibre. The expe- 

 riment is a very delicate one, owing to the minute character of the 

 hairs. The hairs, when moistened with water, appear to divide 

 themselves into two portions, and from each longitudinal half, a 

 fibre, rather indistinctly spiral, protrudes from the apex of each 

 division, or if the hairs are broken, is propelled through the fracture, 

 and sometimes from the base of the hairs. During the propulsion 

 of this fibre, the detached hairs are vigorously swayed to and fro, 

 apparently in consequence of the internal force which accompanies 

 the emission, the stream of tissue rapidly moves from base to 

 apex, and extends to two or three times the length of the indivi- 

 dual hair. The same phenomenon is met with in a few other 

 plant-hairs, but I have not at present been able to solve the pro- 



