164 BOTANICAL GAZETTE [AUGUST 
Observations 
The results of previous workers as to seasonal changes were 
substantially confirmed. Although fat is evidently most abundant 
in the winter months, it is by no means absent during the summer, 
but at that time it is apt to be masked by the starch. Micro- 
chemical evidence as to the relative abundance of either starch or 
fat at different seasons is necessarily unreliable. It is certain, 
however, that much of the starch which disappears in the fall does 
not become converted into fat, but changes to glucose or some other 
non-visible substance, since in many starch trees large numbers of 
cells are emptied of starch without causing the appearance of fat. 
The twigs of some trees, notably species of Catalpa, are almost 
emptied of visible food reserves of all sorts during the winter. 
There are marked differences between species in their ability to 
produce fat, as indicated by its abundance in the phloem and 
cortex. This type of food substance seems to be practically 
absent in species of Carya and is very small in amount in Fraxinus, 
Acer. Syringa, and others. It is particularly abundant in such 
forms as Liriodendron, Populus, and Pinus. In general, fat is less 
abundant in the phloem and cortex of starch trees than of fat trees. 
There are certain exceptions to this rule, however; notably Lirio- 
dendron, a starch tree, but rich in cortical fat; and the soft birches, 
fat trees, but poor in cortical fat. Fat was universally found to be 
more abundant in the phloem than anywhere else in the plant. 
The observations of others that seasonal changes are more 
marked in twigs than in larger branches and trunks was confirmed. 
This conservatism is apparently still greater in the roots, where 
starch was found to be practically unreduced in amount during the 
winter, a fact recorded by Preston and Puttuips (4). In the root, 
too, the amount of fat is very much less than in the stem. 
FapRictus (1) and others have noted the fact that starch trees 
are predominantly hard-wooded species and fat trees soft-wooded 
ones. This rule was in general confirmed by the present study, but 
a number of exceptions were noticed which we shall later find to be 
significant. The hard pines, for example, are clearly fat trees; 
and Liriodendron, Magnolia, Ailanthus, and Platanus, all soft- 
wooded, are clearly starch trees. 
