4°2 P. Q. KEEGAN [december 



entering into solution in the cell sap ; Tout 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. Bather 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, I am 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 evergreen 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- 

 phyllian 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, e.g. 

 Scotch fir, birch, alder, poplars, lime, Bobinia ; 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, etc., is very rich in starch, it, even before 



