402 PO. TLE GAIN [DECEMBER 
entering into solution in the cell sap; but the quantity thereof must 
be extremely small, perhaps not much more than sufficient to forefend 
the utter and final extinction of the feeble spark of life that continues 
to glimmer amid the bitter cold and benumbing surroundings. More- 
over, although it is recognised that ferments are the products of cells 
in process of disorganisation, there is some doubt whether even this 
process goes on in the dead waste and middle of winter. Rather a 
universal torpor seems to reign in the domain of plant life, and, in a 
general way, “as you were” is the word of command from November 
till March. On these grounds, therefore, and for other reasons too 
abstruse to be succinctly recited, Iam disposed to conclude that the 
winter period of rest, even in our evergreens, does actually and prin- 
cipally (I do not say entirely) depend on the external conditions to 
which the plant is subjected. In the case of the Coniferae, their 
limitation of growth towards the north is due to dry winds on sunny 
days in winter stimulating transpiration at a time when the roots can 
draw no fresh supplies of moisture from the frost-bound soil. Hence 
in the everereen leaves of this order, special protective contrivances 
against excessive transpiration are indispensable. In our deciduous 
dicotyledonous growths, on the other hand, these special defences are 
apparently incompatible with that full and free activity of the chloro- 
phylian protoplasm in summer which is necessary to build up 
characteristically hard woods. 
Descending now to particulars, it is proper to mention that what 
Fischer has termed fat-trees are those which are soft-wooded, and con- 
tain at the period of the starch minimum in winter (December, 
January, and February) no starch at all in the rind, wood, or pith, eg. 
Scotch fir, birch, alder, poplars, lime, Robinia; in spruce fir, larch, yew, 
juniper, etc.,the wood never becomes completely devoid of starch, but even 
in these fat predominates in the wood in winter. Starch-trees, on the 
other hand, are hard-wooded, and while in winter the starch dis- 
appears completely from their bark and pith, it remains almost 
unchanged in quantity in the wood and medullary sheath. The 
ultimate cause of these differences seems to be that the assimilatory 
activity of the foliar organs of the trees in the first category is not so 
active as it is in those of the other. More starch is produced in the 
leaves of the latter, the starchy reserves of the medullary rays and 
wood parenchyma are more redundant and not so readily exhausted ; 
hence vitality is more developed, the annual rings are broader, and the 
excess of plastic substance is used up in the thickening of the autumn 
zone of wood, the whole contributing to raise its density and hardness 
considerably as compared with that of firs, pines, and other fat-trees. 
My own investigations lead me to consider that the wood of conifers is 
very poor in starch at all times, even in isolated trees developed in the 
highest noon of summer; while again, although at this season the 
wood of birch, alder, lime, ete., is very rich in starch, it, even before 
