202 NATURAL SCIENCE. March. 



Agencies," he endeavoured to show that the direct action of the 

 environment, coupled with the responsive power of protoplasm, were 

 the sole and efficient causes of the forms of flowers ; the object of the 

 present work is to substantiate those statements for vegetative 

 structures, " so that the two books taken together, it is hoped, will 

 furnish a tolerably complete proof that the origin of all plant structures 

 issues from self-adaptation to the environment (directly or indirectly), 

 without the aid of natural selection." 



There are twelve chapters. The first is introductory ; in it the 

 writer states his case and draws his conclusions. The rest are 

 occupied with an account of the structural peculiarities of plants 

 growing under certain conditions, such as desert plants, arctic and 

 alpine, maritime and saline, aquatic; of climbing plants; of subter- 

 ranean stems and roots ; and of leaves. 



We can recommend the book. Mr. Henslow has been at great 

 pains to bring together a large number of facts, which will interest 

 and instruct the reader and convince him that plants are more plastic 

 organisms than he had probably imagined. But we do not think his 

 opinion as to the value of natural selection will be at all influenced 

 thereby. Before he has got through many pages he will be struck 

 with the fact that Mr. Henslow's arguments may sometimes be used 

 against his theory. For instance, in an early paragraph in the intro- 

 duction on " The Supposed Requirements of Natural Selection," the 

 author asks if there is any evidence, direct or indirect, that trivial 

 morphological differences are of the slightest consequence to a seedling 

 so as to enable it to survive in the struggle for life. " A seedling," he 

 says, " survives among others solely because it is vigorous." But 

 what is " vigorous " ? In some cases it may mean larger cotyledons, 

 giving it a greater assimilative area ; or a taller stem, to lift those 

 first leaves above its competitors ; or a thicker cuticle, to withstand 

 better the attacks of parasitic fungi, like that which is often so fatal 

 to seedlings, the "damping off" fungus. He then instances several 

 experiments, to which others might be added, that larger seeds will 

 produce stronger seedlings than smaller seeds. That is to say, trivial 

 differences in the seeds from the same capsule, such as in size or in 

 amount of stored nourishment, or in a thinner or thicker seed-coat, 

 are of great importance to the embryo in its development to form a 

 seedling, and the experiments quoted by Mr. Henslow do indicate a 

 selection by nature of the resulting seedlings, the basis of that 

 selection being the trivial variations. 



In the next section, on " Darwin's fundamental error," Mr. 

 Henslow refers with regret to the large proportion of Darwin's work 

 which was done on domesticated plants and animals. The evident 

 artificial selections led him to the erroneous assumption of natural 

 selection. On the whole, however, we are not sorry that the author of 

 the " Origin of Species " was attracted to the study of the variations of 

 plants and animals under domestication. Had it been otherwise his 

 greatest work embodying his greatest idea might never have been 

 written, and biology might have had to wait for someone else to give 

 it the enormous impulse which has followed its publication. 



Many botanists will admit that Darwin did under-estimate the 

 action of the environment, and Mr. Henslow does good service in 

 bringing together a large number of facts in evidence of such action ; 

 but it is possible to recognise this and still to leave ample room for 

 the action of natural selection, even though we cannot go and sit 

 down in a field and observe nature in the act of selecting before our 

 very eyes. 



