334 BOTANICAL GAZETTE [NOVEMBER 
when the flowers were allowed to remain attached to the plant. When detached 
there was no increase during the opening of the corolla. Leaves of Ampelopsis 
tricuspidata gathered September 17, October 1, and again on November 2, 
showed a progressive increase in total organic acids during the autumnal redden- 
ing. When allowed to redden detached from the plant, there was no accumula- 
tion of acids. Small plants of buckwheat, when germinated in the dark, showed 
a steady increase in total acids until the eighteenth day after germination. 
When exposed to light during this time, a red pigment developed in the hypo- 
cotyl axis, but no corresponding increase in total acids was found, either in 
plants attached to or detached from the parent stock. Miss KOHLER states 
that this fact may mean that the destruction of organic acids formed in this 
case is greater than their production. 
It is to be regretted that Miss KoHLER has not included some similar deter- 
minations upon leaves which remain green under certain conditions and which 
redden under certain other conditions, in order that a comparison might be 
made. There is some doubt in ine reviewer’s mind that titration of ash, after 
incineration of plant tissue, gives an approximate value of the combined organic 
acids in the tissue before pce. Plant tissue is a complex material. 
Salt combinations other than those of organic acids with inorganic bases may 
be altered greatly by incineration, and may leave a basic ash. Organic acids 
may as well be combined with organic bases within the plant and both would 
be lost on heating. There is even the possibility of a mixture of inorganic 
salts becoming more basic upon heating in a muffle. There is a tendency 
toward accumulation of mineral salts as the leaf ages during autumn, accord- 
ing to Partapin."® This accumulation might account for an increase in 
basicity of ash independent of color formation. In the same way migration 
of mineral salts into corollas and subsequent use of certain anions such as 
sulphates, nitrates, and phosphates in building complex compounds connected 
with reproduction may leave basic elements which combine in various ways 
and which would increase basicity of ash upon incineration. On account of the 
many criticisms which might be justly directed against this method of determi- 
nation of combined organic acid, and on account of the insufficiency of our 
knowledge of complex plant compounds, it is hoped that the author of the 
paper will continue her studies, including some corollas which do not redden 
at the time of opening, and some leaves which do not redden in autumn, 
together with goa methods for quantitatively determining the acids in 
question.—J. M. Arruur. 
Vegetation of Lower California.—<As the result of an expedition conducted 
by members of the United States Bureau of Biological Survey in 1905 and 1906, 
* PALLADIN, V. I., Plant physiology. p. 83. 6th. ed. transl. by LivINGSsTON, 
B. E., 1917. 
