PLANTS MULTIPLY BY MEANS OF STEMS. 
17 
of the brook, but up the stream. Had not the low gi’ound 
been covered with a dense growth of grass, some of these 
branches might have started new trees where the wind 
had left them . 1 
The branches on slow-growing limbs of cottonwood 
and large-toothed aspen are mucbr enlarged at the nodes, 
and at these places are brittle, often separating from the 
tree and breaking up into pieces. Under a small cotton- 
wood were picked up a bushel or more of such limbs, all 
yet alive. These trees are common on low land, and, like 
snap-willows, the severed twigs may find a chance to grow 
on moist soil . 2 
In a greenhouse a potted plant of Selaginella emiliana (?) 
was placed on the bench near the aisle, where it was often 
brushed by people in passing. Small branches, not being 
firmly attached, were frequently broken from the main 
plant and fell upon the moist sand, where they rooted in 
abundance. 
1 C. D. Lippincott believes that this is a provision of nature to dispose 
of the now unnecessary branchlets without leaving a knot. Plant World , 
Yol. I, p. 96. 
2 The brittle branches of salix were noticed by the author in Bull . Torr. 
Bot. Club , Vol. IX (1883), p. 89. 
