1918] CURRENT LITERATURE 463 
It would seem that such marked changes as were found in the reaction 
of the juices of active tissue must affect considerably the metabolic processes, 
as well as the physical condition of the tissue. CROCKER’ has suggested that 
these changes may be important in the regulation of transpiration by succu- 
lents. The lower Values are of the same order as those reported in the same 
work by HEMPEL and also quoted from WacGNneER for non-succulent plants. 
Such P, values range from 5.4 to somewhat above 6. Slightly alkaline juices 
are reported by Haas (/oc cit.) in the petals of certain flowers; he finds, however, 
that blue pigments by no means always indicate an alkaline reaction. 
As the title suggests, the principal object of the work was to gain some 
information as to the substances in the plant juices which act as buffers, or 
regulators of their reaction. On the acid side of the neutral point the following 
data were obtained for this study: (1) titration to the litmus end point (Pg=6.8) 
compared with the original Py value; (2) qualitative tests to determine the 
organic and inorganic acid radicals present; (3) ash analyses to determine the 
total base present; (4) studies of the reaction and titration values of malic acid 
salts, and such mixtures of them as appear likely to occur in the plant. The 
data are most complete for the juices of Rochea falcata, Cotyledon obvallata, 
and C. linguaefolia. The conclusion is reached that in these plants, and prob- 
ably in all succulents, the concentration of hydrogen ions is determined by the 
relation between the quantities of acid and normal malate present. 
On the alkaline side of the litmus end point the data may be grouped as 
follows: (x) titration from the litmus end point to that of phenolphthalein 
(Pu= phone 9.2); @) determination of nitrogen and in some cases phosphorus; 
(3 ) titr ith alumin m malate; (4) titratio with 
wn and verable cous ea ak at the Sere OER point. 
It is concluded that aluminum malate and the unknown substances men- 
tioned are the principal buffers in this region. The nitrogen and phosphorous 
compounds have very little effect. The Hivatioti to the phe erRT end 
point is admitted to be very unreliable. It seems unfortunate that as con- 
siderable quantities of the juice were available ~ slectromerc method of 
titration was not used. Such results would have co uch to the com- 
pleteness and accuracy of the data—THomas G. PHILLIPs. 
Mutationists and selectionists.—JENNINGS® has attempted to reconcile 
the views of the “mutationists” and the “selectionists.”” The latter, headed 
by Caste, have claimed that selection can modify unit characters, and 
presented striking evidence on the point. The mutationists have then demon- 
strated that these data may also be interpreted by assuming that there is but 
7 Crocker, Wa., Rev. Bor. Gaz. 64:526-527- 
* JENNIN se > Modifying factors and oul allelomorphs in relation to 
the results 5 we Amer. Nat. 51: 301-306. 1 
Sok chanel in hereditary Tra hea in relation to evolution. Jour. 
Wash. Acad: Sei 7:281-301. 1917. 
