INTER'CALARY. .\ supplementary day or month. See CAL•Novit: Itissvxrit.E; 1,RAP•VEAR. IN'TERCEL'LULAR SYSTEM (from Lat.
infer, between Neo-Lat. Cc 11111ft, ell/111f% ill 11111111i ive of Lat. cc/la, cell). The system of spaces in plants, often emainims, the cells. They may be formed by the splitting of cell walls (schizogenously ) or by the breaking down of masses of tissue Ilysigenotisly). Spaces formed by splitting are found only in the higher plants. and do not occur at all in plants below the mosses. When a tissue is very young, its cells are angular and in such close emit:let that there are no intervellular spaces; bat as the cells grow older they may become rounded, and the common \•ans may split it the angles, thus produ •ing intercellular sprees of various extent. When the spaces are very large, as in the stems of water-lilies (Nyinpluea), they are called 'air chambers.' Smaller intercellular spaces are al
most universal in the spom,ry parenchyma of leaves. in the pith of steins. and in older paren chyma generally. To this eategory belong many glandular like the resin-ducts of eonifers, the Int•ilage-ducts of eyeads, the gain resin duets of the umhellifers, etc. formed by the breaking down of masses of tissue give rise to the hollow stems of grasses rind many other plants. The cavities in the leaves of quillworts ( Isoctes) and many other plants are also formed in this way. The oil-glands of the orange rind lemon, many glands on leaves which appear to the naked eye as 'pellucid dots,' the gum-cavities in the tissues of cherry-trees, are all examples of lysigenously formed glands. See ANATOMY of PLANTS; .\ ERATION.