LECT. XI.] CAULINAR AND FOLIAR APPENDAGES. 661 



the organ. In Bignonia the vessels appear more 

 condensed, forming one large central fascicle. 

 The epidermis in both is studded with minute 

 fibrils like the radicle ; and these are the real ad- 

 hering organs when the claw is applied to any 

 solid body ; for the adhesion is not confined, as in 

 Cissus, to a knob at the point of the organ, but 

 extends over as much of its surface as is in contact 

 with the body to which it adheres. 



Some writers have classed with this descrip- 

 tion of prop the small tubercles, or absorbing warts 

 (haustoria), by which a few parasitic plants, for 

 instance the Dodder, Guscuta, fix themselves on 

 other plants. But these warts are of a mixed 

 character, performing, under all circumstances, 

 at the same time, the functions both of an attach- 

 ing prop and of a nutrient absorbing organ. 



c. The bladder (ampulla*). This is a small 

 membranaceous bag attached to the roots and the 

 immersed leaves of some aquatic plants, render- 

 ing them buoyant: on which account I have placed 

 it among the props. In shape, the bladder is ge- 

 nerally globular ; but in common Hooded Milfoil, 

 Utricularia vulgaris, it is pear-shaped. It con- 

 tains a watery fluid and a small bubble of air, 

 which enables it to give buoyancy to the parts to 

 which it is attached ; and which must be either 



* Linnaeus terms it a follicle. " Folliculi sunt vasa acre 

 " distenta." Phil. Dot. 163. ix. 2. 



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