Igor] BRIEFER ARTICLES 357 
development of a few members, their growth will be stimulated: while 
robbing it of plastic material or the chance to form, it results in a 
stunted growth. 
Part III, on the annual period of growth of stems and leaves, is the 
most valuable part of the paper. Meissner shows by measurements 
that the chief growths in length of stems and needles fall at different 
times. In Pinus the stem almost finishes its season’s elongation, while 
the needles remain relatively short, the relations in Abies and Picea 
being just the reverse of this. The dry weights of stems and needles 
at various times during the months of growth vary in general with the 
lengths. A moment’s reflection will satisfy anybody who has seen 
evergreens grow that Meissner is correct. Transitory unfavorable 
conditions early in the season will therefore tend to hinder the growth 
of the stem of Pinus more than that of the leaves. The maximum 
growths of stems and needles at different times is a physiological 
explanation of the cases in which short year’s-stems bear long nee- 
dles, or vice versa. But while this makes exceptions intelligible, I am 
by no means ready to agree that there is no connection between the 
Sizes of stems and needles, or that Kraus and I were wrong in expect- 
ing both to vary, in nature, with the general condition of the plant. 
Neither of us could have thought of maintaining that leaves and stems 
could never vary independently ; that external factors, such as light, 
must directly influence both alike. Trees do not respond at once to 
changes in the weather to such an extent that they will often be 
Stunted in May and thrive in June, or grow luxuriantly in May and 
then abruptly halt. At least my observations on the whole resultant 
growth indicate that they do not. 
The influence of bad conditions on the stages of growth previous 
to active enlargement has been left largely out of account, and may 
appropriately receive a word here in the light of Meissner’s results. 
Nn my paper the area of cross sections of the needles was given, and 
was always least the season following transplanting. The difference was 
due to the size of the cells, the number not being materially different 
from that of other years. Thus in leaves of Pinus Austriaca (cf. doc. 
cit. p. 433) the number of cells in cross section was as follows: 
1895 1896 1897 
PRIN Wo ue cekaas ot 176 | 176 | 246 
Outer parenchyma layer..| 77 7 96 
Bndodermisc.4 3...2250% 39 38 48 
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