LIFE-HISTORY OF HEMILEIA VASTATRIX. 381 
year-old plant would possess about 350 leaves, if all were present. 
From data obtained by counting the leaves on a one-year-old 
plant, I find about 66 a common number, and on two-year-old 
plants about 250 to 260. 
On Sept. 23 I carefully examined the young tree once more. 
15 leaves present on Sept. 8 had now fallen, most of them 
diseased, and all among the oldest; and the terminal buds of 
the latter date had each produced its pair of leaves, which were 
still small however. We may therefore consider that the manu- 
facturing eapacity of the tree was little altered, if at all, by the 
Féplscoment of 15 old leaves by 22 young ones ; for although the 
latter could do little at present for the tree, the former could 
not be looked at as of much use either. 
On Oct. 15 the tree, like its neighbours, was becoming badly 
“ diseased,” the yellow spots appearing on the leaves at all points. 
The actual number of leaves present —274; and of these 70 were 
young, and had been formed in the interval Sept. 23 to Oct. 15, 
while 46 leaves had fallen under the devastating action of Hemi- 
leia. Nevertheless, we may here well imagine that the 70 new 
leaves largely compensated the loss of 46 older ones; only, in 
comparing this remark with the statement before made, we must 
keep two facts before us—1st, the destroyed leaves in this case 
were more directly destroyed by the fungus; and 2nd, many 
Spots, that is, masses of mycelium, were now present on the 
foliage yet on the tree. 
On November 9 there were 254 leaves SE of these 46 
were newly formed since October 15. In the interval 66 leaves 
had fallen, badly diseased. 
On December 25 the disease had Seu the mastery to à 
terrible extent; only 50 new leaves had been formed, whilst 107 
had fallen im. The actual number of leaves on the whole 
tree =197. Thus after little more than three months, during 
which period the tree had formed no less than 188 new leaves 
and lost 234, the total number of leaves present were fewer than 
at the commencement, although the possible leaf-bearing area was, 
of course, much increased during the interval. Moreover, these 
fewer leaves were to a great extent badly diseased. The experi- 
ment does not contradict what has been said as regards the seasons, 
since the trees were only planted out (and exposed to the wind- 
blown spores) in June. 
Other facts come out if the above records be carefully studied. 
