50 BULLETIN 1380, U. S. DEPARTMENT OF AGRICULTURE 
thick heavy evergreen leaves may sometimes be almost obscured by 
these patches. The two following species were more or less com- 
mon on Hevea. 
GREEN-SCURF DISEA8E 
In the disease known as green-scurf {CepJwIeuros virescens 
Kunze) the patches are slightly raised above the surface of the 
substratum. In later stages a false epidermis is formed, which 
fuses with that of the leaf. The patches consist of a lobed or 
branched thallus, composed of cells arranged in rows radiating 
from the center. The patches are at first smooth and gray-green 
with small black spots (PL XVII, A), and they are usually very 
firmly attached by means of branched rhizoids. Later, the surface 
is covered with numerous erect septate orange-colored hairs, some 
of which terminate in sporangia and some as sterile projections. 
The sporangia, green when young, orange when old, are carried 
by the wind or rain to other leaves or plants, where they give rise 
to motile biciliate swarm spores (zoospores). These may swim 
about in a drop or film of water and start new colonies. The algal 
colonies are frequently parasitized by fungi. 
The sj:>eeies has been noted on a number of plants in the Tropics. 
Among them are Persea gratissima, Achras zapota, BiscJwffia japon- 
ica, Chrysobalanus icaco, Cinnamomum camphora, Citrus auranti- 
folia, O. limonia, Gardenia jasmin oides, Hibiscus sp., Magnolia sp., 
Mangifera sp., Ocotea leucoxylon, Psidium guajava, and Viburnum 
tinus. 
On the leaves of Hevea guyanensis the colonies may sometimes be 
very conspicuous, but on //. brasilien-sis, owing to the more delicate 
structure of the leaves, the alga) are not so noticeable. 
On the twigs the patches may attain a diameter of 5 millimeters 
or more, but they rarely spread uniformly over the surface. The 
organism is epiphytic and causes little more than a brown spotting 
of the substratum directly beneath the patch. The effect is rarely 
visible on the lower side of the leaf. 
RED-SCURF DISEASE 
The species causing the disease known as red-scurf (Cephaleuros 
parasiticus Karst.) differs from G. virescens in being a true parasite, 
living entirely within the tissues of the host plant (entophytic). 
The disease first makes its appearance as small translucent spots, 
usually on the upper side of the leaf. The alga then spreads 
through and fills the cells of the host, causing hypertrophy and 
death of the tissues. On the lower side of the leaf the spots are 
usually more elevated, irregularly lobed at the margins, and appear 
purplish red through the grayish epidermis of the host (PL XVII, 
D). On the upper side of the leaf the spots are purplish red, 
becoming black and sunken in the center with an irregularly lobed 
red or purple margin. In old stages the spots on the upper side 
have the appearance of dried blood. The epidermis is ruptured on 
both sides of the leaf and the stalked septate sporangiophores bear- 
ing the sporangia appear. These form a yellowish to reddish hair- 
like coating over the spot, or they may be grayish when old. The 
