f mechanical resistance on the develop 
ingame nt and life period of cells. 
ee nice C. NEWCOMBE. 
(Continued from page 157.) 
‘i 
ffect of mechan 
3 . 154) that the © Be h row- 
inted out (p. : oining the g 
pa a extension in the tissue ser at homogenous 
= oo delay the differentiation eae ie oe cause 
tie oe eedians It is also ae alaee aonaaiean 
issue in ditcdy wale age 
later changes w ir elemen 
ee et. by which some Bes sen 
develo ed into mechanical xylem an : . of plants have re- 
ee Oung stems of various Species e that the primary 
ceived fot a internodes at ee ee as to mark off 
differentiation of tissue had proceede ch Intevnaded te cen ce 
fascicular from fundamental, and su 
and it must be 
is not due merel 
because no cell 
seen that the ¢ 
the casts retai 
responding on 
has in al] Cases 
in their pri- 
Myrrhis odorata thicken the ate walled secondary 
"ary bundles and form a wide band of a e a thick-walled 
in normal Parts of their stems pete the stem con- 
, sPears in any bundle in the op of thie plant mee 
YSypsum. A typical preparation. ot n the thickening 
Show the effect of the confining cast ‘thin the cast had 
Walls of vessels:-an average bundle wi | 
ed 
also to 
of the 
