GROUPS OF TISSUES, OR TISSUK-SYSTEMS. 57 
with the external air through the breathing-pores and the 
intercellular spaces of the leaves. 
Fig. 36.—Intercellular spaces. 4, in leaf-stalk of a Water-lily; s, star-shaped 
cells. B,in stem of a Rush: the cells hereall star-shaped. Both cross-sections, 
Fia. 87.—Transverse sections of young stem of Ivy (Hedera helix). A, youn; 
intercellular gum-canal, surrounded by four cells; c, cambium; B, fully devel- 
oped canal, g; b, bast. Magnified 800 times. 
108, Some intercellular spaces serve as reservoirs of gum- 
