36 
BOTANY: E. F. SMITH 
tions to all the others could be predicted by direct measurement from the 
model. 
iMetz, C. W., Genetics, 3, 1918, (107-134). 
2 From measurement of the model, it may be predicted that the cross-over percentage 
between magenta and hairy will be about 4 or 5, and the glazed-rugose percentage about the 
same, probably a little greater. The position of frayed in the system is not fully deter- 
mined, as only two linkage relations of frayed are known. But it may be predicted, from 
measurement, that the frayed-forked cross-over percentage will lie between 39 and 41, and 
that frayed-glazed will lie between 43 and 46, provided of course that the relations given in 
table 1 have been determined with sufficient accuracy. 
THE CAUSE OF PROLIFERATION IN BEGONIA 
PEYLLOMANIACA 
By Erwin F. Smith 
Laboratory of Plant Pathology, United States Department of Agriculture 
Read before the Academy, November 18, 1918 
The cause of the excessive production of adventive shoots on the leaves 
and internodes of this plant (a very strange phenomenon) is attributed to 
excessive loss of water, due to woundings or other causes. Usually in regen- 
eration the response is not far from the place of injury, here it may be at a 
long distance from the wounded part, e.g., roots wounded and response in 
the top of the plant, although a direct response from the injured part can 
also be obtained. The paper will be published in full in The Journal of Agri- 
cultural Research. The following is a synopsis: 
1. Ordinary begonia leaves when detached from the plant and pegged down 
on moist sand develop roots and shoots from cut places and this method is 
used by gardeners for the propagation of begonias. Many other plants are 
propagated in this way, e.g., the hyacinth from bulb scales. 
2. But the leaves and shoots of this begonia proliferate while still attached to 
the plant. 
3. They will proliferate on the plant very freely when wounded, making 
small forests of shoots on the thickened red lips of the wound if the wounds 
are made in quite young tissues, but not otherwise (young leaf blades were 
used). 
4. They will frequently proliferate in the top parts of cuttings (on leaves 
and internodes) especially if the cuttings are dried for a day or two before 
planting. 
5. They will proliferate most astonishingly at the top of the plant (both 
from leaves and internodes) if the roots are wounded, but here again only 
quited young tissues can be shocked into the production of such shoots. This 
is the most striking fact I have discovered, viz., that the prolification may 
occur at a long distance from the place of wounding and must be frohi young 
