ro1t] CURRENT LITERATURE 79 
Digitalis which has been noted occasionally for nearly a century, and which 
was described by CHAMisso in 1826 under the name D. purpurea heptandra. 
The characteristic features of this form consist of a dialysis of the corolla and 
staminody of three or more of the petals, thus producing flowers having most 
typically 7-9 stamens, and scarcely to be recognized as a Digitalis flower at 
all. The degree of development of these characters is variable, and somewhat 
influenced by the environment, but there is no real transition to the normal 
. This form proves to be like the peloric variety, a Mendelian recessive 
to the normal. The reviewer has also been studying the inheritance of this 
peculiar variety for five years, and has reached the same conclusion. Miss 
SAUNDERS confirms the results of KEEBLE, PELLEw, and JoNEs as to the color- 
characters.—GEo. H. SHULL. 
Water relations of desert plants——FitTtInc"’ has studied the water rela- 
tions of the plants growing on the Sahara. He finds, as Livincston found 
for the Arizona desert, that the water is generally gained from the surface 
layers of the soil and not by deep rooting. Many of the plants, especially 
the perennial shrubs not provided with water-storage organs, develop remark- 
ably high osmotic aay which enables them to withdraw water from the 
ee dry soil. On the other hand, the annuals showed much lower 
motic pressure, with lack of ability to thrive in the most exposed places. 
In many cases the high pressures were due largely to stored NaCl, but fre- 
quently entirely to other solutes. the 46 species studied, 21 per cent 
showed an osmotic pressure exceeding 100 atmospheres; 35 per cent exceeded 
53 atmospheres; 52 per cent, 37 atmospheres; while only 11 per cent showed 
osmotic pressures as low as 11 to 22 atmospheres. Species showing extremely 
high pressures in dry desert conditions show much lower pressures in moist 
situations. This marked power of certain plants to adjust their osmotic 
pressures to the water-withholding power of the medium in which they grow 
has been demonstrated for salt marsh plants by H1L1," a piece of work which 
Firtinc does not cite. We have known little about the osmotic pressure of 
desert forms, and this work supplies much of the deficiency and makes rr 
character of great significance in the physiology of these forms.—WILL 
OCKER. 
Permeability.—SCHROEDER”® has studied the semipermeable membrane 
of the wheat grain, and confirms the work of Brown on the barley, but adds 
little that is new. The portion of the coat forming the semipermeable mem- 
7 Firtinc, Hans, Die Wasserversorgung und die osmotischen Druckverhiltnisse 
der Wiistenpflanzen. Zeitsch. Bot. 3: 209-275. 1911. 
Hirt, F. G., New Phytologist 7:133-142. 1908; Rev. in Bot. GAzETTE 
472170. 1909. 
*9 SCHROEDER, H., Ueber die selektiv permeable Hiille des Weizenkornes. Flora 
102:186-208. Ig11 
