The Origin of Floral Structures. " The International Scientific 'Series."
By Rev. G. Henslow. (Began Paul and Co.)—The Rev. George Henslow prefers to follow Saint Hilaire's monde ambiant as the primal cause of change, and refers the origin of floral structures to environment. To him, insect agency seems to have played by far the largest part in forming floral organs and appen oes. The formation of hairs he endeavours to trace to the irritating action of insects, also the honey-glands, though why they should secrete sugar no one has been able to show, as he confesses. As was to be expected, the writer has gone deeply into the technology of botany, and has embodied in the present volume a great deal of original research. We may instance the chapters, ." Development of Floral Whorls," " Degeneracy of Flowers," " Progressive Metamorphoses," " Diclinism," and " Varieties of Fertilisation." The writer, in casting about for a term which shall explain the relation of cause to effects, has concluded with Professor Huxley that what is essential is "a good theory of variation." The objection to " natural selection " given by Mr. Henslow seems to him
an insuperable obstacle, i.e.,—" The greatest difficulty lies, firstly, in the fact that the struggle for life takes place in the seed- ling stage, before any varietal or specific characters have appeared. Secondly, granting that the plant has survived till the flowering period, why should so many minute details of floral structures be necessarily correlated ?" More numerous cuts would have added to the value of the volume.
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