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as they are or are not in sympathy with the environment. In 

 Prof. Henslow's view heredity entirely prevails, and it is the 

 environment " that directly inspires whatever variations may 

 occur. In a general way this is obviously true. The ** environ- 

 ment'' that gardeners supply has wrought a multitude of varia- 

 tions in cultivated plants, while in nature, under extreme condi- 

 tions o[ heat and cold, dryness and moisture, fertility and sterility, 

 tne offspring of a single plant may easily, in one generation, vary 

 almost beyond recognition. For a single instance, how often 

 have merely "depauperate" forms been reckoned as distinct 

 varieties, or even species! But is the ''environment" potent 

 enough to have evolved the existing multitude of floral forms, 

 ranging from the simple flowers of Ranunculus to the highly 

 complicated ones of Orchis and Asclepias? Prof Henslow 

 answers with a bold affirmative. While conceding that ''to some 

 extent the attempt must be regarded as speculative," he aims 

 ' to refer every part of the structure of flowers to some one or 

 niore definite causes arising from the environment taken in its 

 Widest sense '' (p. xi.). No originality is claimed for this view. 

 The author's avowed object is to go back to 1795 and revive 

 Geoffroy St Hilaire's '* conditions of hfe" {^nonde ambiant) as the 

 *' primal cause of chancre/' 



slo 



Of all the factors concerned in floral development Prof Hen- 

 vv reckons insects as by far the most active and influential. 

 Protoplasm promptly responds to the stimulus oi mechanical 

 irritation, especially in such sensitive tissues as those of flowers. 

 Phe punctures and pressures and thrusts and tensions of insects, 

 repeated and continued through succeeding generations, are held 

 to have developed nectaries, produced hairs, enlarged petals, 

 lengthened stamens, and otherwise modified floral organs in an 

 endless variety of ways. In "galls" and similar morbid plant- 

 growths we have constant evidence of the effect of insect irritation 

 11^ stimulating and diverting the action of protoplasm. The 



fasciated leaves common in Solidago furnish another striking 

 example. Still more notable are the *' leaf-cones " of some 

 species of Salix, "probably occasioned by the puncture of 

 insects" (Gray, Manual, p. 462.) The present writer has repeat- 

 edly opened these cones without being able to find any larva or 



