RUBBER (HEVEA) DISEASES 35 
fandiana Hub. (Para), H. spruceana Hub. (Obidos), and II. col- 
Una Hub. (Parintins). It is to be remarked that all of these col- 
lections are from the lower Amazon. The fungus also was found 
sparingly on trees in the Botanical Garden at Para labeled as 
follows: "II, brasiliensis, H. coUina, and H. spruceana." On the 
label of the type specimen of Dothidella at Para the host is recorded 
as H. patudosa Ule. 
The fungus is reported on Hevea confusa in British Guiana and 
on H. guyanensis in Dutch Guiana, and it was found sparingly on 
R. guy art ends at Manaos. It seems that the type of the leaf of 
this host may be more resistant than the mors delicate leaf of 
H. brasiliensis. The fungus is an obligate parasite and is highly 
specialized on Hevea. Xo other host is known. As is the case with 
most true parasites it will not grow on artificial media. 
LIFE HISTORY OF THE FUNGUS 
The life history of the fungus includes three distinct spore forms. 
They are, in order of production, conidia, pycnidia, and ascospores. 
The fungus first makes its appearance on the young leaves as 
they unfold from the bud, or two or three days afterwards, or at 
an} 7 time before the leaf reaches maturity. The severity of the 
infection, however, becomes less with the increase in age. Trans- 
lucent spots, which soon become olive or blackish green, appear on 
the young leaves. These spots are usually at first scattered either 
along the edges or promiscuously over the entire surface but may 
soon coalesce, until the entire leaf surface is involved. The edges 
then begin to roll, and the entire leaf crumples up, becomes black, 
and hangs limp from the twigs as though recently scorched bv fire 
(PI. XV, A). 
At other times onfy a portion of the leaf at the edges or at the tip 
or in the region of the glands at the base is infected. The unequal 
stress caused by the continued development of the uninfected parts 
tears and splits the infected portion, so that it may fall away or leave 
irregular holes extending toward the midrib. The leaf then may 
present a very ragged appearance, rolling inward from the edges 
and upward from the tip, so that the leaves on a twig may be bunched 
or snarled. Finally the leaflets fall, usually leaving the petioles at- 
tached. When the infections occur sparingly on the leaf and do net 
coalesce, owing to the rapid development of the leaf, the infected 
tissues become discolored and fall out, with the resulting shot-hole 
effect. It is evident, that the conidial stage of the fungus is 
dependent upon the early developmental stages of the leaf tissues; 
otherwise leaves four or five days old when first infected would be 
entirely involved. The following uncontrolled experiment further 
illustrates this point. A quantity of conidia-bearing leaves taken 
from a plantation at Para was carried during a period of heavy rain 
into the near-by jungles and laid over the leaves of a young wild tree 
3 feet high bearing leaves in different stages of development. The 
very youngest leaves showed infection in three days* time. The 
older leaves remained free from the disease. The rapidity with 
which young unfolding leaves during rainy weather may be infected 
is surprising. Leaves observed to be unfolding, hanging vertically 
with their edges adhering, due to the excessive atmospheric moisture. 
