30 
Ohio Naturalist. 
[Vol. 1, No. 3 
and expense to drop twig and all than to separate every individual 
leaf. Possibly in the Cottonwoods, with their large leaves, we have 
a survival of the Tamarisk twig-shedding habit long after its 
original significance has disappeared.” Dr. Bessey, however, we 
believe, will not insist on this supposition when he considers that 
the same thing occurs in species of Primus, Quercus, and other 
widely separated genera. 
Fig. 1 — Twig of Populus alba, showing large basal joint and scars where smaller twigs 
have been detached. 
Fig. 2 — View of basal joint of same twig as Fig. 1. 
Fig. 3 — Twig of Salix nigra, showing position of the brittle zone (rt). 
Fig 4 — Green twig of Ampelopsis cordata, showing joints (a) at the leaf nodes. 
The self-pruning of twigs from woody stems, so far as our 
observations go at present, is accomplished in three general ways: 
1st. by the formation of a single joint close to the parent branch; 
2nd, by the formation of a brittle zone near the base of the limbs 
which are to be shed ; 3rd, by a series of transverse joints corres- 
ponding to the leaf nodes. 
