1894.] The Influence of Mechanical Resistance. 153. 
of this meristematic tissue when its growth is mechanically 
checked. In none of these cases were the experiments con- 
tinued till the death of the cambium, and hence the duration 
of its vitality, when its growth is mechanically prevented, is 
still undetermined. Pfeffer, in the work mentioned, states 
that the root-tips of Vicia faba in casts remained alive for 
five weeks, but that at the end of ten weeks had begun to die. 
The cambium certainly lives longer under similar conditions. 
Cucurbita pepo with considerable growth of stem outside the 
cast and very few changes within the cast has preserved its 
cambium for sixty-six days. Eryngium planum and Ligust- 
icum Leguari about whose stems casts were placed at the 
time the cambium ring was completed, grew well afterward, 
forming outside the casts normally thick stems, and at the 
time the plants were taken for examination had produced 
seeds; the cambium was thus preserved in these species for 
seventy days. Young plants of Vicia faba grew after the 
second or third epicotyledonary internode had been encased 
Nn §ypsum to a size and development equalling normal plants 
and had seeds partially formed when the plants were cut for 
*xamination 116 days after placing in gypsum. Dahlia var- ~ 
ve does not grow very well when a cast is put around a 
a stem. Several individuals however added half a 
fave 0 their height and were still growing and had healthy 
ni ng cambium within the cast 138 days after the begin- 
ing of the experiment. Pterocarya fraxinifolia, Juglans 
ar criment was continued for seventy days, at the end 
conditions OR the cambium appeared normal. In similar 
OF ninet ri with similar results Sambucus nigra was grown 
tolacca “to days, Ricinus communis for 100 days and Phy- 
stem, ther ws for 197 days. In the last named plant, in one 
bial derives: ni been formed within the cast five or six cam- 
gun, while is in a radial row after the experiment was be- 
cells had 1. oY 2nd below the cast thirty to thirty-five such 
It j ad been formed. 
itiacs i understood that in all these cases the stems- had 
Sreatly in diameter beyond that of the part within 
