Rhodochytrium spilanthidis Lagerh.

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Reprinted from the Botanical Gazette 46: 299-301, October

WEW YOR1
BOTANICA
GARDEN

BRIEFER ARTICLES

Wittrock et Nordstedt. Algas exsiccaüv.

1096. Rhodochytrillin Spilanthidis Lagerh.

In Bofc. Zeit. 1893.

JíquatorisB a. in foliis caulibusque vivís Spilanthidis sp. in monte
Panecillo prope Quito 18T¥89;

b. in eadem matrice in monte Ichimbía prope Quito 18\°92.

Professor G. Lagerheim.

A PARASITIC ALGA, RHODOCHYTRIUM SPILANTHIDIS
LAGERHEIM, IN NORTH AMERICA

During February, 1908, Dr. F. L. Stevens, of the North Carolina
Agricultural College, sent me a few dried leaves of the common ragweed,
Ambrosia artemisiaejolia, which contained a very interesting parasite.
Externally it suggested the appearance of a Synchytrium, because of the
numerous minute red dots distributed beneath the surface on the petioles
and veins of the leaf and on the stem, although there was no gall forma-
tion similar to that caused by species of the Synchytriaceae. A section of
the host, however, showed clearly that it was very different from any of
the members of this family. Maceration or teasing of the host tissue
revealed the presence of a mycelium, and the crowded condition of the
fruit bodies suggested the genus Cladochytrium. Further study proved,
however, that it was a unique type, very different from members of this
genus. Since the material received was dead, it was impossible to obtain
the zoospores, and Dr. Stevens kindly promised to have fresh material
sent me at stated times during the summer.

Beginning,in the month of June, material was collected by Mr. J. G.
Hall, assistant in botany at the North Carolina Agricultural College, and
mailed once a week. Entire plants were collected, the roots were washed,
and then packed mostly in pasteboard boxes with wet sphagnum. In this
way they reached me in two or three days after shipment in very good condi-
tion, so that some of the parasitized ragweed plants were transplanted in
the open and others in pots where they continued to grow.

From a study of this material I have been able to obtain the zoospores
from the temporary zoosporangia and to work out certain stages in the
life-history of the parasite. While searching the literature for unique
forms of plant parasites, I discovered that this plant had been described
fifteen years ago.

This remarkable parasite is Rhodochytrium spilanthidis Lagerheim.1
It was first discovered by Lagerheim in 1889 near Quito, Ecuador, and
later was observed by him in other provinces of Ecuador. In Ecuador it
is parasitic on the stems and leaves of a species of Spilanthes, one of the

1 Lagerheim, G. de, Rhodochytrium, nov. gen., eine Uebergangsform von den
Protococcaceen zu den Chytridiaceen. Bot. Zeit. 51:43~53- 2- *893.

299]	[Botanical Gazette, vol. 46

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