192 The Botanical Gazette. [May, 
in a radial row twelve thick-walled vessels, twenty-eight thin- 
walled; above the cast in the same stem in an average bundle 
the thick-walled vessels were forty, the thin-walled twelve. 
A shoot of Sambucus nigra that had grown for several weeks 
with a cast around one of its internodes had when examined 
a secondary zone of cells within the cast as well as out of it. 
Within the cast and a little above the cast the number of 
cells in a radial row of this zone was eighteen, the same in 
each case. But in the former only three cells had thick walls, 
while in the latter there were six such. Similar results to the 
foregoing were obtained in Urtica dioica, Dahlia variabilis and 
Forsythia viridissima. No contrary effect was obtained in 
any plant. 
In experimenting on the effect of pressure on the develop- 
ment of thin-walled phloem into hard bast the results will 
perhaps be more striking, since in the plants selected the 
hard bast is of primary origin and the casts were not applied 
till the very cells destined for the fibres were present in the 
thin-walled condition. Hence in such cases certainly the pos- 
sible factor of the interference of the cast with cell-division 
and so with the final result is eliminated. 
een days after a lower internode in each had been mage 
walled cells, while above and below the casts hard ses i 
Present as well as thick-walled xylem. Other individu fifty 
the same species, which after similar treatment grew for 
days, had begun within the casts to thicken the walls 
bast cells. Urtica dioica, grown for twenty-three day 
application of casts, had within the casts no ‘ 
bast, but considerable in the normal adjoining inte 
Other individuals, after growing under the same eee 
of treatment as these for fifty days, had developed 
ditions 
