354 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



A few points seem to call for a little correction. Four " circum- 

 stances " promoting transpiration are mentioned but the most im- 

 portant — red and violet rays of light — are omitted. " Warm air " may 

 induce evaporation, but transpiration is a function of light, whereas 

 respiration is effected by heat. It is true that " respiration is a 

 wasting process," but it should be added, it is the means in all organic 

 beings of liberating energy, as for plant work (see 'Linn. Soc. Journ.' 

 xxii. 81 and xxix. 288). 



Twenty-seven examination papers, set at some of the principal 

 colleges in the British Isles, conclude the volume. 



" The course of work," writes the author, " followed in this book 

 is directed in the main to the establishment of the fundamental prin- 

 ciples of Plant Physiology. . . More space has been devoted to Ecology 

 than is usual in an elementary text-book. . . . The subject-matter 

 covers the work necessary for " — the examinations referred to. Lastly 

 it contains 257 excellent photos and text-figures, as well as a copious 

 index. 



In one respect the book is too good, for many young people 

 (unless they are properly trained to observe living plant-structures) will 

 be tempted to "get up " their botany from this book alone. We 

 have gone through all the questions in the twenty-seven papers, 

 and rarely find one which cannot be answered out of this excellent 

 manual. 



But to be " too good " for the few would be no reason for elimi- 

 nating a single line for the many. If there is a weak point desirable 

 to point out, it is one commonly found in modern text-books which 

 introduce Ecology ; namely, that while admirably describing the 

 correlations of plant-structures adapted to the external phenomena 

 of plant associations, the writers suddenly stop short of the most im- 

 portant and obvious inference, which we will give in the words of our 

 two great ecologists, Schimper and Warming. The former says : 

 " The change [of existing floras] is due. . . to a transformation of the 

 plants . . . their structure is subject to a process of metamorphosis 

 . . . being rapidly modified by changes in the environment . . . 

 constituting the ' adaptations ' in which the external factors acting 

 on the plants are reflected." This agrees with Darwin's statement 

 that the " direct action of changed conditions of life produces ' definite ' 

 variations, without the aid of natural selection." Schimper, then, 

 concludes his paragraph: "The investigation of these causes of 

 differences ... is to be numbered among the chief duties of 

 geographical botany " (Preface to " Plant-Geogiaphy " &c). 



Dr. Warming strongly corroborates this view : "It is beyonddoubt 

 that characters peculiar to growth-forms have arisen through direct 

 adaptation to the environment, . . . and these acquired characters have 

 been fixed by heredity " (" (Ecology," p. 373). Our author, in describing 

 the " Work of the Root," alludes to external " stimuli," observing 

 they " are important factors in the environment of a plant ; and, as they 

 vary frequently, it is necessary for the plant to respond and adjust 



