233 



NOTES ON THE TEASELS, DIPSACUS SYLVES- 

 TRIS AND D. PILOSUS, AND THEIR 

 NATURAL RELATIONSHIP. 



By J. FRENCH. 



[Kfad Deceinbey 2nd, lSgo.\ 



'"PHE Teasel, Dipsacus sylvestris, in its stage of flowering and 

 seed is so familiar that description is quite unnecessary. Dip- 

 sacus pi/osus, with a more modest appearance, is less common, and 

 not nearly so well known. Its heads of flowers are nearly globular, 

 and not half the size of those of its kinsman, and the bloom is white 

 and inconspicuous. The plant, moreover, is nearly destitute of that 

 formidable array of prickles so characteristic of D. sylvestris. The 

 curious arrangement of water-cups in the latter plant, which are 

 developed at the axils of the leaves at an early stage of its growth, is 

 absent in D. pilosus. In point of foliage and habit the two plants are 

 not greatly unlike. 



We will now call attention to the prickly apparatus and cups of 

 D. sy/vestris. Neither of these appliances are brought into operation 

 until the stems' are in process of development. The cups precede 

 the prickles, which latter do not appear on the stem until the fourth or 

 fifth node is reached. The cups, hoivever, cease just before the time 

 of flowering, while the prickles are hardened and multiplied to a 

 much later date. 



A very cursory examination will assure us that the cup is the 

 result of a special process, and is not the accidental result of con- 

 tiguity of leaf bases like Blackstonia, Lonicera, and others. Long 

 before the leaf attains its full development the puckering at the base 

 is well marked, and a set of vascular vessels specially contributing 

 to the support of the cup make their appearance. The rim of the 

 cup, too, is very entire, and never crenated like the leaf limb. The 

 cups are absolutely water-tight, only losing water by evaporation and 

 rupture. 



The arrangement of the prickles is such as to indicate a special 

 design. This design is more pronounced as the plant advances to 

 seed, and in the species known as the " Fuller's Teasel " {D./ulIotium) 

 it attains its maximum. The points of the prickles are directed dowiv 

 wards, as though to repel a foe creeping upwards. In the " Fuller's 



I The plants are. it shoiikl be recollected, biennial, .nnfl in the first year make only radical 

 leaves. 



