332 BOTANICAL GAZETTE [APRIL 
states that it is abundant in Denmark, growing mostly in large close com- 
munities. Its gregarious habit is due to the activities of horizontal rhizomes, 
which also account for the sharpness of the boundaries separating it from other 
vegetation. It thrives well in full light, and in shade up to 5-10 per cent of 
open daylight, the greatest vigor being shown in 10~20 per cent of full illumina- 
- tion. A moderate amount of soil moisture also seems necessary to meet its 
requirements; but while OLSEN has determined the percentage of soil moisture 
in the habitats under consideration, he has not attempted to determine the 
growth water available. 
By several authors Urtica dioica has been placed among nitrogen-requiring 
plants, and the principal feature of this investigation was the experimental 
re) 
to obtain an expression of the nitrifying power of the soil. These data were 
tabulated, together with the hydrogen-ion concentration, the percentage of 
soil moisture, and the light value of the locality. The table makes it evident 
that the only factor varying directly with the presence of Urtica dioica is the 
nitrate content of the soil 
Experimental cultures of the plant were made, using portions of rhizomes 
successfully with other vegetation only where there is a relatively large amount 
of nitrogen in available form present in the soil. The experiment also showed 
that nitrification proceeds in soils showing an acid reaction as high as Pu=3.-6, 
and that ammonium used as a source of nitrogen was toxic to the nettle.— 
Geo. D. FULLER. 
Pink root of onions.—Another of the many diseases directly attributed by 
farmers to alkali in the soil has recently been shown to be due to a parasite, 
as a result of investigations carried on in the Texas Experiment Station.‘ 
Isolation and inoculation studies have definitely connected a species of 
Fusarium, tentatively called F. malli, with the pink root disease of onions. Over 
twenty-five species of fungi were found in diseased plants, including several 
species of Fusarium, and the association of some of these fungi with F. malli 
increased the virulence of the latter. All varieties of onions and garlic 
5 TAUBENHAUS, J. J., and MALLy, W., Pink root disease ah onions and its control 
in Texas. Texas Agric. Exp. Sta. Bull. 273. PP. 42. figs. 3. 
