THE MATERIAL OUTGO OF PLANTS 
339 
cane sugar, are known to be re- 
tained ordinarily by the cyto- 
plasm ; yet nectar glands secrete 
sugar one or more times. Others, 
for example enzymes, have a com- 
position which, though imper- 
fectly known, is such as to suggest 
that the cytoplasm would usually 
be impermeable to them; yet di- 
gestion occurs in such places as to 
make it certain that enzymes are 
able to pass out of the cells in 
which they arise. 
-x 
FIG. 033. Section through a 
petal of buttercup (Ranunculus), 
showing nectar gland (n) and 
shallow receptacle formed by 
the " nectary " (a). Note bundle 
of conducting tissues (*). 
After BONNIER. 
FIG. 634. Flower of nastur- 
tium (Tropaeolum ma jus) cut 
through the middle to show the 
spur (s) and the nectar (n). 
FIG. 635. Nectar gland in the 
Ovary of day lily (Hemerocallis 
fiava). After ScHNiEWlND-THiES. 
