456 BOTANICAL GAZETTE [DECEMBER 
in addition to the growing point, namely the fascicular cambium, 
the pericycle, and the cork cambium. Srmon? finds that in regener- 
ating root-tips the pericycle is the active layer. In Zamia the peri- 
Fic. 4.—A chip from the cortex 
a has ear a new shoot and 
x §. 
cycle is poorly differentiated, and 
does not act as a secondary cam- 
bium, as is the case in Cycas and 
certain other cycadean genera. 
In the cases observed the new 
shoots nearly always arise from 
the wounded surface; and as a 
layer of wound-phellogen is always 
found beneath this surface it 
must be added to the list of 
active regions. It has been im- 
possible thus far to secure the earli- 
est stages in this adventitious 
shoot-formation, but sections 
through moderately young  re- 
gions of this kind show the layer 
of callus curving outward around 
the base of the shoot-primordium 
(fig. 7). This suggests that the 
phellogen forming the callus is 
responsible for the initial growth 
of the new shoot. If this be 
true, a new shoot may be pro- 
duced at any point of the surface 
covered by the callus. In fact, 
in the cases of Zamia before us 
the new shoots stand over either 
fascicular cambium or cork cam- 
bium, but this position seems to 
us to be favorable rather than 
essential to shoot-formation. 
A case of the production of adventitious shoots from the hypocotyl 
2Simon, S., NERS iiber die Regeneration der Wurzelspitze. Jahrb. 
Wiss. ai 40: 103-143. 
