308 



MB. E. IRWIN LYNCH ON BRANCH TUBERS AND 



/ 



Mr 



when the whole is composed of two intercedes. The formation of 

 the tuber never takes place up to the growing point ; there is 

 always a short portion of stem which falls away, with also one 

 or two leaves of stunted development. 



The tendrils of this vine are of great interest, on account of their 

 having adhesive disks already formed without the stimulus of con- 

 tact with any substance, two such plants only 

 being recorded by Mr. Darwin in his highly 

 interesting work ' Climbing Plants.' One of 

 these at least, Vitis or Ampelopsis Veitchi ( V. 

 tricuspitlata), is entirely dependent on its disks 

 for climbing-support, while this species can, and 

 does sometimes, entirely dispense with their 

 aid. The adhesive disks are so rarely formed 



by the tendrils of 



Darwin has observed only four species and re- 

 ferred to two others. AVe read of Bignonia 

 capreolata (I. c. p. 102), "If the hooked 

 extremities of the tendrils do not touch any 

 thing, disks, so far as I have seen, are never 

 formed ; but temporary contact during a mode- 

 rate time suffices to cause their development." 

 Then, in a footnote, that Fritz Miiller states that 

 in South Brazil the trifid tendrils of IIoplolo- 

 pliium (one of the Bignoniacea)), without having 

 come into contact with anv substance, termi- 

 nate in smooth shining disks ; and that these, 

 after adhering to any object, become conside- 

 rably 



ftedcracea, the Virginian Creeper, Mr. Darwin 

 says that the '* disks are never developed, so 



enlarged. 



"With regard to Ampelopsis 



Tendril of Vitis 

 gongylodcs. 



far as I have seen, without the stimulus of at On piece of Bam- 

 least temporary contact with some object ;" boo, showing at 



d, d the enlarge- 

 ment and attach- 

 ment of disks, at 

 c,c cellular adhe- 

 sive layers, and 



contact with any object ; and that he has since a t e a disk un- 

 observed the same fact. At p. 179 we read enlarged. From 

 that u The rapid development of these adherent y° un 8 8p^ imen 

 disks is one of the most remarkable peculiarities growing at Ke*. 



adding, in a footnote, that Dr. M'Nab remarks 

 (' Trans. Bot. Soc. Edinburgh,' vol. xi. p. 292) 

 that the tendrils of Ampelopsis Veitchi bear 

 small globular disks before they have come into 



