Growth and Striicture of the Wood of Larix . 631 
formed in one year. For though in a multiple ring the successive bands of 
autumn wood often run together in places (as in PL L, Fig. 13), and so unite 
to form a single ring round the rest of the circle, in a partial ring the circuit 
is completely interrupted for a greater or lesser extent. Now even in 
undefoliated trees rings may be partially or wholly absent from the base of 
the trunk if growth becomes stunted through overshading or unsuitable 
soil. 1 When therefore a similar result is observed to follow on defoliation 
it can only be referred to the same cause — lowered vitality brought about 
by starvation. 
A priori it might be objected that annual differences of temperature or 
rainfall might minimize the value of comparisons between the growths of 
successive years. Table I, however, for a tree that had never been 
attacked, shows that the influence of such climatic variations has been quite 
insignificant during the last six years. Of the other examples for which 
measurements are given two more came from this same area in Central 
Wales, while three are from the neighbourhood of Thirlmere. And since 
all the trees examined were of much the same age (from thirty to forty-five 
years) and were all planted at much the same altitude (500 to 650 feet), 
there remain no good reasons for supposing that the defoliations have not 
been the chief or even the sole factor in causing the reduction both of the 
breadth of the whole ring and the proportion of autumn wood. 
Of course the effects of defoliation vary in intensity according both to 
the severity of the attack and to the vigour of the tree at the time. Despite 
repeated defoliations the trees B, C, and D were reported to be still flourishing 
when they were felled, and only in one of these, C, were rings at all absent, 
and then only in the lower parts. Table VI, on the other hand, represents 
a tree that was dead at the time of felling, like two others for which 
measurements are not given, and in all three of these dead trees growth had 
ceased entirely at the base one or more years before they were felled, 
though the upper parts still formed a ring each year. Between the upper 
parts, where the cambium still remained active, and the lower parts, where 
it had become quiescent, the partial rings already described were of frequent 
occurrence. The tree F (Table VII) was said by a competent authority 2 
to be dying when it was felled, and certainly it shows at its base the same 
absence of rings as the three dead trees just mentioned. It would seem 
from these examples that where vitality has reached so low an ebb that 
growth quite ceases at the base, the tree is not likely to be able to withstand 
another defoliation, even though it is still growing at the top, as in Table VII. 
But as long as it is still growing at the base it would seem to have sufficient 
reserve food-materials left to enable it to put forth further crops of leaves 
season by season until it may ultimately outlive the present infestation by 
the Sawfly. Nevertheless, in all the cases investigated the attack has 
1 Cp. Hartig (2), p. 4, and Nordlinger, p. 9. 2 Mr. R. L. Robinson. 
