jiLY in, 1003.] 



SCIENCE. 



53 



" 5. Proper Freedom — freeilom from meehaiiioal 

 and other disturbances which would interfere with 

 its supply of food, water, warmth and light, and 

 prevent it from carrying on its natural functions." 



And again, under the heading ' The Livins 

 Matter and the Actively Living * Structure,' 

 the author says: 



" As Hertwig has so strongly emphasized, the 

 living and active protoplasm is to be regarded not 

 as a chemical compound or an association of 

 chemical compounds, but rather as an orderly 

 arrangement of these into a definite structure, of 

 which water is an indispensable constituent. Some 

 of the water contained within the cell should be 

 considered to be as much a constructive con- 

 stituent of the living protoplast as the water is 

 of the crystal of copper sulphate. As, without 

 a certain amount of water, one can never .have 

 crystals, no matter how much copper sulphate 

 may be present, so also, without the necessary 

 amount of water we can never have active proto- 

 plasm. When the water of constitution is with- 

 drawn, all the activities of the cell cease with the 

 demolition of its structure." 



In the carrying out of the author's plan he 

 devotes one chapter to nutrition, another to 

 absorption and movement of water, still an- 

 other to growth, one to irritability and one 

 to reproduction. In the chapter on the ab- 

 sorption and movement of water the author's 

 treatment of transpiration is interesting. 

 Thus, on page 136, we find the following: 



" From all their surfaces exposed to the air, 

 plants give off water-vapor. This is a physical 

 necessity, for water-vapor will be given off from 

 any mass, lifeless or living, which contains water, 

 whenever the surrounding air is not saturated 

 with moisture, or when the mass has a tempera- 

 ture higher than that of the air, or when the 

 mass, in relatively dry air, is not enclosed in a 

 waterproof covering. Other things being equal, 

 the amount of water-vapor given off will be 

 greater the greater the exposed surface in pro- 

 portion to the mass. With like conditions of 

 humidity, temperature, surface-composition and 

 surface-area, equal masses of different composi- 

 tion, will dry, i. e., lose water by evaporation, at 

 different rates, a gelatinous or slimy mass more 

 slowly than a woody one, for example. The liv- 

 ing plant differs from a dead one of exactly the 

 same dimensions in being able to control four of 

 these five factors, and to that degree it is able 



to control the rate and the amount of evaporation. 

 Because evaporation from the body of the living 

 plant is controllable within certain limits by the 

 plant itself, and to this extent is a physiological 

 process, it has been given the separate name of 

 transpiration." 



After a little further discussion he says: 

 ' Transpiration is, therefore, a physical process 

 controlled but not carried on by the living 

 plant. According to circumstances it may 

 be more or less rapid than simple evaporation.' 

 This view of the nature of transpiration is 

 one which the present reviewer has held for 

 many years, contrary to the views of many 

 of the older physiologists, and it is gratifying 

 to find that Dr. Peiree holds this physical 

 view of the transpiration process. 



In passing we notice with interest what the 

 author has to say with reference to ecology, 

 to which he refers very briefly on pages 252- 

 253. Of it he says : ' Meantime it is more 

 or less the fashion under the name of ecology 

 to view things in the large way, and by feel- 

 ing rather than by the application of exact 

 physiological methods, to reach conclusions 

 regarding the effects of environment and of 

 association.' We gather from this that the 

 author has little use for the looser ecological 

 methods, and in this again the present re- 

 viewer must heartily agree with him. 



The volume is full of original suggestions, 

 and differs quite markedly from the old-time 

 works devoted to plant physiology. We con- 

 gratulate the author upon the success which 

 we are sure must attend the publication of 

 this book. Charles E. Bessev. 



ThK I'XIVKRSITY OF XF.nU.\SKA. 



CaferpiUars and their Moths. By Ida 

 Mitchell Eliot and Caroline Gray 

 SouLE. New York, The Century Com- 

 pany. 



In this handsome book of more than three 

 hundred pages we have a very valuable con- 

 tribution to the literature of popular ento- 

 mology. The authors have mapped out for 

 themselves a special field and have occupied 

 it to excellent advantage. The caterpillars 

 chosen for treatment are those of the larger 

 moths, especially the more common ones, no 



