402 BOTANICAL GAZETTE [NOVEMBER 
state that ‘‘all questions connected with the relation between true self-fertility 
and self-sterility have been omitted designedly as pertaining to a distinct prob- 
lem.” Are we unreasonable in asking for a single theory to explain both self- 
fertility and self-sterility ? Are we wrong in thinking that the significance of 
self-sterility lies in its relation to self-fertility? Such a general theory, no 
doubt, will be provided by the authors in their later reports; the present pub- 
lication evidently represents merely the first of a series on the general subject 
of self-sterility 
he explanation also has another theoretical shortcoming, similar to that. 
which applied to East’s “heterozygosis.” In heterozygosis East stated that 
hybrids are vigorous because of their heterozygous sets. This virtually 
amounted to saying that hybrids are vigorous because they are hybrids. 
“Heterozygosis”’ was a more accurate and scientific statement of the fact of 
hybrid vigor, but it was not an explanation. Now East states that pollen will 
not function on stigmas of a plant of which the germinal constitution is the 
same as that of the plant which produced the pollen. Couched ina terminology 
involving multiple allelomorphs and crossing over, this may well be a more 
accurate and scientific statement of the facts of self-sterility and its behavior 
in inheritance, but it is not an explanation. Such scientific restatements are 
very valuable in helping to organize facts, and “‘ heterozygosis”’ unquestionably 
had such a value. The present theory, however, seems at first sight a muc 
less valuable one, since it is so elastic as to be confusing. 
But whether the theoretical argument of the authors is destined to stand 
or fall, they have done an exemplary piece of research. This seems to have 
COULTER. 
Buffer processes in succulents.—JENNY HEMPEL‘ has made a very impor- 
tant addition to our rather limited knowledge of actual reaction in plants. 
Succulents were used in this work, since, with their well known wide and rapid 
variations in acid content, they might be expected to supply especially interesting 
material for such astudy. Determinations by the use of the hydrogen electrode 
were made on the juices of numerous specimens of the plants studied, after 
they had been exposed to varying conditions. The values found range from 
Pu=3.9to Py=5.7. Higher acidity than the more acid of these values is re- 
corded in the same work in lemon juice (Py=2.19); and by Haas’ in citrus 
fruits (Py=2.22-3.8), in cranberries (Py=2.4), and by a less exact method 
in the petals of certain flowers (Py=about 3). 
‘HempeL, Jenny, Buffer processes in the metabolism of succulent plants.. 
Compt. Rend. Trav. Lab. Carlsberg 13:1-129. 1917. 
’ Haas, A. R. The reaction of plant protoplasm. Bor. Gaz. 63:232-235- 1917- 
——,, The acidity of plant cells as shown by natural indicators. Jour. Biol- 
Chem. 27:233-241. 1916. 
