14 
PLANT MORPHOLOGY. 
There are also colors found in plants other than those 
already described, which are not due to the pigments 
associated with plastids, but are caused by blue, violet 
or purplish coloring principles dissolved in the cell 
sap. The white appearance of flowers is attributed to 
the inclusion of air in the cell sap. 
C. UNORGANIZED CELL-CONTENTS. 
The unorganized constituents of plants may be said 
to differ from the organized cell-contents in two im- 
portant particulars, namely, structure and function ; 
that is, they are in the nature of direct or indirect 
products of the latter. For convenience in consider- 
ing them here, they may be grouped as follows : 
(1) Those of definite form which may be further 
divided into (a) those which are colloidal or crystal- 
loidal, as starch and inulin ; (b) those which are non- 
colloidal or crystalline, as the sugars, tannin, alkaloids, 
glucosides, calcium oxalate; (c) composite bodies, as 
aleurone grains, which are made up of a number of 
different substances. 
(2) Those of more or less indefinite form, including 
gums and mucilages, fixed and volatile oils, resins, 
gum-resins, oleo-resins, balsams, caoutchouc, and also 
silica and calcium carbonate. 
I. SUBSTANCES MORE OR LESS DEFINITE 
IN FORM. 
(a) COLLOIDAL OR CRYSTALLOIDAL. 
1. STARCH. 
Starch is the first visible product of the constructive 
metabolism 1 of the plant. This product is found in 
J By metabolism is meant those chemical changes in the organism 
whereby complex substances are formed from simpler materials, 
or even the elements themselves ; or from complex compounds 
simpler ones are formed. The former is known as constructive 
