248 
The Ohio Naturalist. 
[Vol. XIV, No. 4 , 
down as is fixed in the construction of these materials, i. e., that 
the complete oxidation results in a quantity of water equal to that 
required during photosynthesis and chemosynthesis, the amount 
of water comprises but little more than three-fifths or 60 to 65 
percent, of the weight of the dry matter of plants. The ecological 
water requirement it will be seen is greatly in excess of the actual 
quantity of water used; the quantity of water lost by transpira¬ 
tion is not related to the synthetic process. Transpiration aids 
the gaseous exchange, but the rate and amount of CO, entering 
is not in proportion to the water evaporating through the stomata. 
The diffusion of the gas is independent of it, and the supply of CO, 
is usually less than could be utilized by the chloroplasts. The 
results obtained in green and dry weight of plant depend upon and 
vary within the limiting conditions of the C0 2 gradient in the air. 
the light intensity, and the general temperature conditions as 
well as the duration of period of the growth. 
Unfortunately the number of investigations on hydrolytic 
reactions in plants during their entire life cycle is small, and it 
would be therefore unsafe to make any extended discussion of 
the results. The greater percentage of organic matter in tissues 
is often due to hydrolytic reactions, but the total quantity of 
water used in this manner is unknown, since no means are yet 
available for the determining the extent and the degree of hydra¬ 
tion, and the number of times which degradation or metabolic 
transition products function in hydrolytic reactions. In many 
cases the action consists merely in an absorption of water which 
is followed by a splitting up of the substance. The different 
hydrolytic enzymes which act upon glucosides, and such catalytic 
agents as saccharase, amylase, cytase, lypase, protease are active 
in this stage of metabolism. In other stages the hydrolytic pro¬ 
cesses are reversible and accelerate synthetic combinations, some 
of the products showing profound differences in reaction and with 
relation to the influence of external factors. The number of such 
intermediate compounds is large; their molecular structure is not 
sufficiently well known, and the knowledge of this construction 
action is yet very scanty. Hydrolytic reactions occur in all 
stages of growth, from germination to maturity and decay. 
The attention of physiologists has been attracted thus far 
especially to the dependence of these reactions on temperature. 
However, the principle of temperature coefficients fails to hold 
rigidly, for wherever components are co-ordinated into a system 
of reciprocal relations, and obscured by the effects of limiting 
conditions, such as in the cycle of changes collectively spoken of 
as growth, the character and the rate of any one single reaction 
is not that of more elementary chemical processes. Beyond a 
certain point, further temperature increases do not cause more 
growth. The favorable range of temperature has not as yet been 
