390 BOTANICAL GAZETTE [NOVEMBER 
rich in pigment it corresponds to a greatly weakened light. In general the 
development of the plant is proportional to the dry matter produced; but growth 
is not exactly proportional thereto, for it is more feeble in strong light and more 
vigorous in weak light than it would seem if it were measured by the augmentation 
of the dry weight. The root and stem are unequally affected; the former grows 
more and the latter less as the illumination increases; but too strong a light 
reduces the rate of growth of both because less food is produced. The develop- 
ment of the leaf blades generally increases to a maximum with decreasing light, 
but diminishes with further enfeeblement. With some exceptions transpiration 
does not have any sensible effect on the total production of dry matter, though 
the quantity in proportion to the fresh weight generally diminishes with the 
diminished light. 
All the green plants are capable of regulating the quantity of light absorbed, 
and so partly avoiding the injurious effect on production of dry matter, by altering 
the quantity of chlorophyll produced. These adaptations are limited in plants 
poor in chlorophyll; but those rich in pigment can adjust themselves to a rela- 
tively very weak illumination. Biologically the massing of plants ought to be 
an advantage by reducing the illumination. Physiologically the action of light 
is not limited to the reduction of H,CO,, for it affects also the speed of incor- 
poration [assimilation] of carbohydrates. The former demands a stronger light 
than the latter, for which there is an optimum, and below and above this it rapidly 
diminishes in rate. It is by this retarding action of bright light upon the incor- 
poration of carbohydrates and a consequent considerable accumulation of foods 
in the green tissues that the diminution in the production of dry matter is expli- 
cable when the illumination passes a certain limit. [This explanation does not 
explain and surely needs further consideration.] If the chemical transformations 
which constitute the incorporation of carbohydrates are of enzymic nature, it IS 
probable that they are affected by the action of light on the formation and destruc 
tion of enzymes. [Is not the fate of the greater part of the carbohydrates ' 
be sought rather in protein synthesis than in “incorporation; ” and is there any 
evidence of enzymic action in this process ?]—C. R. B. 
Self-digestion and endospermic respiration.—The long effort to settle the 
question of the vitality of the endosperm, which was begun by Gris and VAN 
GHEM, Was practically abandoned after the culminating researches of BROWN 
and ESCoMBE, PuRIEwitscH, and Brown and Morris. Since that time very 
little indeed has been contributed to the subject. Perhaps one reason was oe 
the results of somewhat related investigations so modified our knowledge of 
enzymes and respiration that self-digestion as a test of vitality was no longer 
Pegi as valid. Altogether disregarding such opinions, BRUSCHI® takes Se 
Problem practically as it was first attractive fifty years ago, “to solve 
sherds Dana, Researches on the vitality and self-digestion of the eae 
sperm of some Graminaceae. Annals of Botany 22:449-463. 1908. 
