1910] CURRENT LITERATURE 159 
Plant diseases.—WHETZEL and STEWART,*® contrary to the common belief, 
advocate the cultivation of pear orchards if a crop of fruit is desired. In this 
view they are upheld by HeEprick of the State Station, who found that blight 
epidemics are not necessarily dependent upon cultivation and manuring. No 
immunity to the disease was obtained by the use of certain blight remedies. 
SACKETT?7 has described the appearance of this new bacterial disease in the 
field, and has given the manner of infection, together with a complete morphologi- 
cal, cultural, physical, and biochemical description of the causal organism, 
Pseudomonas medicaginis sp. n. The work is well supported by numerous 
inoculations. The only thing lacking in this well-balanced investigation is a 
bibliography.—VENvs W. Poot. 
Source of nitrogen for molds.—RuitTER® finds that the ammonium salts of 
mineral acids as the source of nitrogen for the molds is inverse to the strength of 
the acid forming the negative ion of the salt. The author attributes this to the 
toxic effect of the acid liberated by the assimilation of the ammonium ion. For 
instance, mono-ammonium or diammonium phosphate is a far better source of 
nitrogen than the ammonium salts of sulfuric, hydrochloric, or nitric acids. e 
so-called “Nitratpilze” (Aspergillus glaucus, Mucor racemosus, Cladosporium her- 
barium) gave on the average a greater yield of organic material from the two 
ammonium phosphates mentioned than from potassium nitrate. The yield from 
the ammonium salts of the stronger mineral acids was very much lower.—W1- 
LIAM CROCKER. 
Excretion of salts by Statice. —SCHTSCHERBACK"® has investigated the excre- 
tion of salts by the leaves of Statice Gmelini. Many leaves of halophytes are 
known to excrete salts in considerable quantities by means of the glands aeacsives 
by DeBary and others. Leaves of Statice Gmelini, floating on pure water, are 
soon freed from their contained salt and thereafter excrete water only. The amount 
of excretion of a leaf floating on a solution of a substance depends upon the sub- 
Stance and the concentration of it used; sulfates and chlorids of sodium, potassium, 
and magnesium tending to increase it, while calcium compounds and sugars de- 
Crease it. The amount of excretion does not depend upon the turgor pressure 
in the leaf cells—R. Catirn Rose. 
Physcia villosa in North America.—In a recent number of this journal (49: 
320. 1910) TI recorded this plant from southern California. Since then I have 
Gaara 
© WHETZEL, H. H., and Stewart, V. B., Fire blight of pears, apples, quinces, 
Bull. N.Y. Cornell Exp. Sta. 272:31-51. figs. 5-231. 1910. 
‘7 Sackett, W. G., A bacterial disease of alfalfa. Bull. Colo. Exp. Sta. 158: 1-32. 
. I-3. O16. 
18 
Ritter, G., Ammo 
Ber. Deutsch. Bot. Gesell, 
ete. 
niak und Nitrate als Stickstoffquelle fiir Schimmelpilze. 
27:582-588. 1909. 
Slaticg TSCHERBACK, JOHANN, Ueber die Salzausscheidung durch die Blatter von 
sslice Gmelini. Beih. Deutsch. Bot. Gesell. 28: 30-34. IgI0. 
