80 ; BOTANICAL GAZETTE [JULY 
factors. Environmental factors were found to have a marked influence upon 
invasion by the parasite (Fusarium), there being a “‘critical soil temperature”’ 
(about 17° C.) for such invasion. Below this the plants are not invaded even 
in the sickest soils—J. M. C 
Desiccation.—An investigation of the course of desiccation and partial 
starvation in cacti has been made by MacDovuecat, Lone, and Brown. The 
principal studies center upon the changing rate of water loss, chemical changes 
in the food reserves, plasmatic colloids and cell sap, and the morphological 
changes which occur during long periods of desiccation. In one case a large 
_ Echinocactus was under observation for 6 years after removal of the plant from 
he soil. Water loss is rather rapid at first, but proceeds more and more slowly 
with time. ile 10 per cent of the water was lost the first year in one speci- 
men, during the sixth year only 5 per cent of the water remaining at the begin- 
ning of that year was lost. The loss of water is much more rapid of course in 
the open than in diffuse light, and Echinocactus can withstand desiccation not 
more than 2 years with free exposure.—GEo. D. FULLER. 
Aeration of nutrient solutions.—StILEs and JORGENSEN* find that aeration 
of the nutrient solution increases the rate of growth of barley, as found by 
various workers, but has no effect on the growth of buckwheat, as found by 
REE. ey carefully limit their conclusion to the condition under which 
they experimented, and find themselves unable to explain this specific differ 
ence. They emphasize the necessity of knowing much more about the physical 
chemistry of water culture solutions. They also feel that neither the law of 
the minimum nor the principle of limiting factors gives an adequate expression 
of the behavior of the plant as a whole—Wwa. CROCKER. 
Apogamy in ferns.—STEIL* has discovered apogamy in a large number of 
ferns, the investigation extending over a period of 6 years. It seems that 
apogamy is of frequent occurrence in Pellaea, Pteris, and Aspidium. The 
prothallis were sealibe under cultural Sendetorss favorable for the development 
mbryos in non-apo Many interesting details 
of embryo pre are given, which mich extend our knowledge of this 
phenomenon.—J. M 
33 MacDoveat, D. T., Lone, E. R., and Brown, J. G., End results of desiccation 
and respiration in succulent plants. Physiol. Res. 1: 289-325. 1915. 
34 Stites, W., and JORGENSEN, I., Observations on the influence of aeration of the 
nutrient solution in water culture experiments, with some remarks on the water culture 
methods. New Phytol. 16:182-197. 1917. 
IL, W. N., Studies of some new cases of apogamy in ferns. Bull. Torr. Bot. 
Club 45:93-108. pls. 4, §- 1918. 
