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TRANSPIRATION AND THE ASCENT OF SAP 149 
eriticism of earlier theories. Naturally a large amount of 
material from that article appears in the present book, but the 
tte 
aan a pull on the water columns in the stem, we are led 
logically to the conclusion that a dead leafy branch kept under 
ordinary conditions should go on draining up water through the 
stem. It can be shown, however, ae while a dead stem will go 
on conducting water for some time if certain promo are 
taken, yet a dead leaf soon shrivels, although it may be in direct 
connection with conducting channels amply supplied with water. 
This difference seenar the behaviour of living and dead leaves 
in no way impu the cohesion theory; it merely shows that 
io 
some vital action is necessary, 7.¢. these phenomena are 
» dent on some physical and chemical relation which ceases to exist 
on the death of the cell. In the present work this point is 
important part in transpiration of water under all conditions. If 
this is so, a vital theory of the ascent of sap is sites the sound 
one, though not in the sense that it was originally us 
In spite of the title of his book the author doate. very briefly 
with transpiration, only one chapter being devoted to that subject; 
there are many interesting problems of transpiration which might 
have been discussed. The author seems to believe in plunging 
his readers in medias res, for the book speais with a statement as 
to the oe water loss from the two sides of a hypostomatous 
leaf; a botanist whose interest was mainly in oe and 
these are still ra the majority, would be likely to be repelled by 
such a ane introduction to the subject. Th the list of papers 
at the end of Chapter 1, of the thirteen references, seven are 
undated. One notices ‘alad with regret that Prof. Dixon should 
lex his name to the misuse of ‘ hypothecate” on p. 51. This 
word, seseee seems to be a special pitfall for men of science, is of 
(on p. 6) why the ~ a of turg Bosvers about ae death of the 
loat-eally should affect the oa of water-loss except by causing 
collapse of the cells. “illcon however, are very small blemishes 
in an admirable book which provides in an accessi a 
account of an extremely important branch of botanical work 
