230 The Botanical Gazette. [June, 
internodes within the casts did not elongate. In these inter- 
nodes the intercarinal canals had not formed in one plant, 
their place being occupied by living cells, while in the other 
plant but two or three cells had died in each of those positions. 
Above and below the limits of the casts the canals were of 
large size. It need hardly be mentioned that normally these 
canals arise mostly by the destruction of cells. Similar pre- 
parations to the foregoing but in which the stems were left 
in the gypsum twice as long, had, when examined, canals 
within as well as without the casts. 
A young plant of Zea mais the lower part of whose stem 
was so encased in gypsum as to prevent elongation of one of 
its internodes to one-third of what it would have been, had 
not within the cast thirty-seven days afterwards formed the 
usual lysigenous canals in the vascular bundles, the thin- 
walled cells being there undisturbed and living, while in other 
parts of the stem they were destroyed. Here since there was 
but slight constriction of stem made by the cast, the prolonga- 
tion of the life of the cells in question is probably to be re- 
ferred to the checking of the elongation of the internode. 
The growth of the leaves of Allium cepa is not easily con- 
fined by a surrounding cast; since, when the tip of the page 
left free the organ glides through the gypsum because of the 
very smooth sutface of the former. This. gliding can be pre- 
vented, however, by bending the leaf into a zigzag CoUurs© 
so fixing it before the gypsum is poured on. By pursuing 
within casts have been kept from becomin 
all cells remained alive. In the same leaves, aD 
low the casts the normal inflation took place twoo 
after the casts were applied. The longest pero 
central cells of such leaves within casts have been ke 
is fifteen days, or from eleven to twelve days after suc 
r three days 
d that the 
pt alive 
h cells 
had died in parts outside the casts. eres ag 
Sachs!* has shown that if an onion is gerne this 
dark, its leaves will not become hollow. Histologica”’ 
the peripheral cells of the young leaf to t 
these assimilating cells that the central hyal 
“4aung uad 
nerntete 1863 
En 
‘4 Sachs: Ueber den Einfluss des Tageslichtes auf New jlage. : 
tung verschiedener Planzenorgane. Botanische Zeitung, Bei 
