306 
ON THE FALL OF BRANCHLETS IN THE ASPEN 
(POPULUS TREMULA). 
By Samvuet G. Suartock, F.R.C.S.* 
Tue ready fall of the branchlets in the Aspen ae tremula) 
is a sufficiently remarkable occurrence among the larger exogenous 
trees to merit a close investigation, and wi ith co object the fol- 
lowing account may not be wholly withioat’ intere 
In the exogenous trees, with scarcely any seo beyond 
those to be noticed, and of which the Aspen is the most remarkable, 
the death of a branchlet is followed, indeed, _by its: ultimate 
the wood of the dead part undergoes changes which render it so 
friable or brittle that :. is readily shaped ge see oss by the first 
_ violence that befals it; if of considerable size, perhaps, by its 
sheer weight. It may be sufficient to say, for = Ane esent purpose, 
that in this eee of usual detachment the living parenchyma of 
the bark, the cork alone excepted, furnishes ey transverse par- 
titioning a line “of cork and underlying phellogen, by which the 
living part = abruptly demarcated off from the dead; in some 
circumstances a similar demarcation ensues in the pith and 
medullary ak the woody prosenchyma and _ bast- sri alone 
ae accent the dead with the living. The parenchyma 
t a ; i i 
dead wood . the same time becomes so brittle fo teaseeien on 
the eth violence aed “ootinplats the separation of "the dead parts. 
The mediate cause Pee this a of the dead wood the 
h 1m 
transformation into wood, at first of a modified kind, and a proper 
cortical system. By the progressive advance of this tissue the 
broken surface, though never healed, is covered in. In this process 
no vital ehanges are set up by whic ch the dead wood of the a 
part is cast off from the living, and the actual surface of the 
Rackared: wood remains unhealed. 
The other process of fall has been named by Berkeley+ ‘“ Cla- 
doptosis.”” In a short communication, one of a valuable series, 
Berkeley notices this fall as occurring in the white arillow and oak. 
I have observed the same in both trees; but he does not mention» 
the Aspen, in which the process is most marked, and the details of 
the process, with which the present communication is me age 
he did not investigate. In the following account I will li 
* Read before the Linnean Society, Jan. 18th, 1883. 
¢ ‘Gardeners’ Chronicle,’ Sept. 8th, 1855 
