226 BOTANICAL GAZETTE [SEPTEMBER 
about infection in one place would probably bring it about in the other. 
Observations made in the field cannot in general be as reliable as those 
made in the greenhouse, where the conditions of temperature and humidity, 
important factors in bringing about infection, are to a greater extent under 
the control of the observer. Observations made in the greenhouse may 
be duplicated from time to time more readily than can be done in the field. 
An example of the rusting of wheat, cited by RoBERts,? seems to indi- 
cate that.an excess of nitrogen in the soil favors rusting. The many field 
observations made by STONE and SmITH,? on the other hand, indicate that 
the physical condition of the soil is an important factor in the abundance 
and distribution of the asparagus rust, the rust being more abundant on 
asparagus grown in light soils with a low water retentivity, and less abun- 
dant on asparagus grown in heavier soils containing more organic matter 
and with a higher water retentivity. 
What are the conditions that produce an abundance of rust, whether 
in the field or in the greenhouse? Are they excessive food supply in the 
form of available nitrogen, the physical condition of the soil, favorable 
conditions for bringing about infection, or some other causes ? There 
cannot be a general distribution or abundance of a rust without a previous 
general infection; and there must have been a previous development of 
Tust spores with which to bring about such an infection and distribution. 
There must have been sufficient food furnished by the host so that the rust 
could mature its spores for distribution and infection. Of course, certain 
conditions of temperature and moisture are always necessary before 
germination of the spores and infection can take place. 
Some results obtained by the writer, in cooperation with the United 
States Department of Agriculture, have already been published in Science.* 
The present results obtained for the carnation ‘rust, when different kinds 
of soils were used, are a continuation of the same line of investigation. 
From previous inoculations of Asparagus, Allium, Dianthus, and Gyp- 
sophila, with the asparagus and carnation rusts, the results obtained 
seemed to indicate that the conditions that were favorable for the devel- 
opment of the host were also favorable for the development of the rust- 
A considerable number of inoculations were made on different species 
of Asparagus and Dianthus. The plants were of different ages and Badass 
in the greenhouse, where they were under control in so far as infection 
was concerned. The results show that the plants that were making @ 
vigorous growth were more susceptible to artificial infection—inoculation— 
- ? Roserts, I. P., The fertility of the land. p. 155. 1897- 
3Stone, G. E. and Suirn, R. E., Ann. Rept. Hatch Expt. Sta. 14/199? 
4SHELDON, JoHN L., Science, N. S. 16:397. 1902. 
