438 BOTANICAL GAZETTE [DECEMBER 
years. On comparatively young trees, I to 5™ high, the leaves 
may fall the second year. Asa rule the average length of life 
may be placed at two years, that is, the leaves fall the summer 
or autumn of the second year. The time of falling, however, is 
not constant, as in some cases it may occur in the spring. 
Numerous physiological changes take place during the 
period of from three to four weeks preceding the actual fall of 
the needles. First, the contents of the mesophyll cells gradually 
disappear, this being accompanied by a change in the color of 
the needle from green to reddish yellow. With the disappear- 
ance of the chlorophyll bodies, large oil globules appear in the 
mesophyll cells, and at the same time the walls of the latter 
become considerably thickened. Not until a week or ten days 
before the pair of needles fall is it possible to make out clearly 
the separative layer, the formation of which does not materially 
differ from that which takes place in most of the ordinary 
deciduous plants. In case of high wind or rain the leaves are 
frequently blown or knocked off before the separative layer is 
fully developed. Usually they remain on, however, until the 
process is fully completed, after which they dry up and fall 
from their own weight. 
DEVELOPMENT OF THE FUNGUS AND ITS EFFECTS ON THE TREE. 
An examination of an affected tree early in April shows on 
the needles of the previous year’s growth pale yellowish bands, 
which vary in width from 2 to 4™". The discolorations seldom 
if ever extend to the extreme tip of the needle, this point as 4 
rule remaining normal in color up to a certain time, despite ne 
action of the fungus on the tissues below. Close examination 
of the diseased areas at this time reveals numerous brown and 
yellow pustules, which are only slightly elevated above the nae 
face of the leaf (figs. § and 9). The pustules are the sor of 
the fungus, and mark the point where the spores will eventually 
break through. The sori vary in width from 0.2 to 0.5"; and 
are from 0.2 to 1™™ long. As the season advances the sori 
increase in size, many of them coalescing and forming long 
