THE STORAGE OF RESERVE MATERIALS 239 
tained in fleshy roots and stems. Many plants belonging 
to the Crucifere and several allied orders are particularly 
rich in reserve materials belonging to this group. Sz- 
- grin, or myronate of potash, is the principal glucoside 
which they contain. It splits up into sulphocyanate of 
allyl, grape-sugar, and hydrogen-potassium-sulphate. 
The nutritive value of these bodies is partly due to the 
sugar which they yield on decomposition. The evidence 
that the other products can minister to nutrition is not 
very complete, though it seems satisfactory in certain 
cases. 
Fats or oils are frequently stored as reserve food-stuffs 
in different plants. The distribution of this material is 
very varied, though, as in so many other cases, the seed is 
the most general place of deposition. Many seeds—that 
for instance of the castor-oil plant—contain as much as 
60 per cent. of their dry weight of oil, which is non-volatile. 
Others contain as little as 2 per cent., and between these 
limits very varying amounts may be found. When the oil 
is in great preponderance, it is usual for no other form of 
carbonaceous reserve to be present; in cases where but 
little oil occurs starch is usually found as well, as in so 
many of the Leguminosae. The Crucifere as a group 
often contain oil in fairly large quantity. As a rule nitro- 
genous reserves in the shape of aleurone grains accompany 
the oil. 
In other places than seeds large deposits of oil often 
occur, though their purpose is not so obvious. We have 
them in large amount in the pericarps of certain fruits, 
such as the olive; in the petals of many flowers, e.g. 
Funkia and Ornithogalum ; in the leaves of some of the 
Agaves, the roots of Oncidiwm, &e. They can hardly be 
regarded in some cases as truly reserve materials, being 
perhaps more strictly connected with the mechanisms of 
dispersion of seeds. 
The mode of deposition of oil or fat is not at all well 
known. It is generally found saturating the protoplasm of 
