not be considered the perfect stage of Thielaviopsis basicola (Berk.) Ferraris any more than of the other fungi above noted. The results with extracts, here recorded, are an additional indication that Thielavia basicola is a distinct fungus and they are also an argument against any ideas of heterothallism that may have been connected with it.

Thielavia basicola Zopf has always been found associated with Thielaviopsis basicola (Berk.) Ferraris on the same hosts. Whether or not it is by itself parasitic on these hosts or, as has been suggested by Dr. Clinton, a parasite on Thielaviopsis basicola, is not yet determined. Inoculations of Thielavia basicola have been made on tobacco in the greenhouse as well as in the field without definite results. The biologic relationship of these two forms is not yet clear.

SUMMARY.

Perithecia of Thielavia basicola Zopf have been secured in artificial culture.

Since the name Thielavia basicola was given by Zopf on account of the presence of perithecia, the fungus secured from their ascospores should be considered Thielavia basicola Zopf. This is the first report of its isolation in artificial culture.

Thielavia basicola Zopf has a tendency to produce perithecia when grown alone, but this is greatly stimulated when the fungus is grown with Thielaviopsis basicola (Berk.) Ferraris with which it is associated in nature.

It has been shown that Thielavia basicola Zopf is also stimulated to produce perithecia when it is grown with Cladosporium fulvum, Aspergillus umbrosus, Aspergillus of the glaucus group, Eurotium amstelodami Mangin, and to a certain extent with Fusicladium pirinum.

It has been shown that Thielavia basicola Zopf is likewise stimulated to produce perithecia when it is treated with water extracts obtained from Thielaviopsis basicola (Berk.) Ferraris, Cladosporium fulvum, Aspergillus umbrosus, Thielaviopsis paradoxa, Saccharomyces cerevisiae and also with a water solution of Taka-diastase.

The above evidence indicates that Thielavia basicola Zopf is not the ascospore stage of Thielaviopsis basicola (Berk.) Ferraris although the two forms are commonly associated.

LITERATURE CITED.

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1876.

EXPLANATION OF PLATES.

Plate XXXVII.

Fig. 1. Violet plants infected with Thielaviopsis basicola (Berk.) Ferraris and Thielavia basicola Zopf.

Fig. 2.

Part of section of infected violet root.
basicola.

P, perithecia of Thielavia

Fig. 3.

Fig. 4.

Fig. 5.

Fig. 6.

Part of section of infected violet root showing sclerotial masses
of hyphae and chlamydospores of Thielaviopsis basicola.
Photographed by Mr. E. M. Stoddard.

Part of section of infected violet root showing perithecia of
Thielavia basicola.

Part of section of infected pea root showing perithecia of Thie-
lava basicola. Photographed by Mr. E. M. Stoddard.
Part of section of infected tobacco root showing perithecia of
Thielavia basicola. Photographed by Mr. E. M. Stoddard.

Plate XXXVIII.

Figs. 1-8.

Figs. 9 and 10.
Figs. 11-22.

Fig. 23.

Germination of ascospores of Thielavia basicola Zopf. Figs. 1 and 6 magnification x 1,000; Figs. 2-5 and 7-8 mag. x 450.

Hyphae of Thielavia basicola Zopf. x 600.

Stages in the development of the perithecium of Thielavia basicola Zopf. Figs. 11-16, 18, 20-22, magnification x 1200. Figs 17 and 19 mag. x 1,000.

An ascus of Thielavia basicola Zopf with ascospores. x 1,200.