BIOLOGY OF ALEURODISCUS 
447 
cated by Burt's report that, in collections from Idaho westward, the echinu- 
late marking of the spores is very faint. 
Another saprophyte of the balsam tree that in the form of its fruit 
body bears a superficial resemblance to Aleurodiscus is Dasyscypha Agassizii 
(Berk. & Curt.) Sacc. The two are often found side by side, and they are 
the first two conspicuous saprophytes that attack the tree. After two or 
three years, when the bark of the twigs becomes somewhat loose from decay, 
numerous other saprophytes are encountered, most common of which are 
Polystictus hirsutus (Wulf.) Fr., P. pergamenus Fr., Lenzites hetulina (L.) 
Fr., Panus stypticus (Bull.) Fr., Creonectria cucurhitula (Sacc.) Seaver, and 
Poria sp. 
Aside from the plants above mentioned, the writer has very frequently 
encountered a small species of Tremella that grows upon the fruit bodies 
of the Aleurodiscus. Indeed, in more than half the cases in which the latter 
were found on fallen balsam trees, the Tremella was present. It appears 
in the form of hyaline glistening droplets on the fruit bodies of the Aleu- 
rodiscus, varying in size from microscopic bodies to forms that completely 
cover the surface of the plant. Cross sections of such fruit bodies harboring 
the Tremella are shown in figures 9 to 11, Plate XXXII. So far as the 
writer knows, the plant is truly parasitic and is confined to this host. It 
was never seen growing on the bark of the balsam fir away from the Aleu- 
rodiscus, nor on the other fungi mentioned above as commonly encountered 
by the side of this one. The Tremella hyphae grow down into the hyme- 
nium and subhymenial tissue of the Aleurodiscus and mingle intimately 
with those of the latter. Beneath the parasite the hyphae of the Aleuro- 
discus soon cease active growth and for a long time remain in a degenerating 
condition before they are killed. It is in this condition that the nucleus 
shows characteristic structures and the cytoplasmic granules undergo 
significant changes that are to be discussed in detail later. 
The writer is unable to identify the Tremella with any species previously 
described. The species that perhaps approaches it most nearly is Tremella 
versicolor Berk., which was described in Europe as "parasitic on Corticium 
nudum on decorticated trees" (Berkeley, 2). This plant, however, is 
described as orange in color, at length assuming a rufous tinge, while the 
one here in question is always hyaline, never assuming even the color of its 
host. The fruit body consists of an interwoven mass of much branched 
slender hyphae (2J 11) which secrete a viscid material that gives the whole 
a gelatinous consistency. When young, and even at the very beginning of 
its growth, its surface is usually covered with abundantly branched conidio- 
phores. The conidia are elliptical in shape, 5 X 7 and stain very densely 
with safranin or haematoxylin. Large numbers of them are often seen 
embedded within the lower parts of the older tissue. A very definite 
hymenium is formed of the globose basidia that divide in the cruciate manner 
characteristic of the Tremellales. This hymenium stands out in the photo- 
