BOOKS KECEIVED, 



589 



"The Fertilisation of Orchids." By Charles Darwin, LL.D., F.R.S. 

 (8vo. John Murray, 2s. Gd, net. 300 pages.) 



A fascinatingly interesting book to the student of Nature, pointing 

 out as it does the endless diversities of structure — Nature's prodigality of 

 resource — for gaining one and the same end. Trifling details of structure 

 are noticed, and their causes and utility investigated, Mr. Darwin's 

 theory being that no diversity from type ever occurs without some direct 

 cause generally related to the benefit of the individual plant as well as to 

 the perpetuation of the species, and from this point of view each trifling 

 detail of structure repays investigation and research. No one who had 

 not studied the matter would for a moment have suspected that such 

 trifling details of structure as Mr. Darwin notices could have been of 

 such intense importance to the life history of the species as he suggests. 



" Vegetable Mould and Earth Worms." By Charles Darwin, LL.D., 

 F.R.S. (8vo. John Murray, 2s. 6d. net, 300 pages.) 



Everybody will welcome a reprint in so cheap a form of Mr. Darwin's 

 most interesting book. He shows us in it that worms have played a by 

 no means insignificant part in the history and formation of the earth's 

 surface, for they bring up to the surface no less an amount of earth 

 (weighed when dry) than ten tons an acre annually, and of this some is 

 washed down by rain into the valleys and some is blown by the wind 

 towards the opposite quarter to that of the prevailing wind, thus gradually 

 but very really altering the general contour of the earth's surface. They 

 are also of the greatest assistance to plant life by periodically turning 

 over the mould, bringing the lower layers to the top, and exposing them 

 to the air, and also by mixing them intimately together as a gardener 

 mixes compost for his plants. By dragging leaves down into their burrows, 

 tearing them in pieces, and partially digesting them, they help to form 

 that dark rich humus which is so valuable for plant growth ; their 

 burrows, sometimes reaching down as much as five feet into the earth, 

 aerate it and assist the passage of young root-growth. 



It is very interesting to find that the subject was first suggested to 

 Mr. Darwin by Mr. Wedgwood, the founder of our Royal Horticultural 

 Society. 



" Plant Disease and its Relation to Animal Life.' By E. F. Wright. 

 (Sm. 8vo. Swan Sonnenschein, 160 pages, 1903.) 



In many ways interesting to a scientific-minded gardener and in all 

 ways to a student of nature. The chief argument pursued by the 

 author runs on these lines : — Iron in the soil is absolutely necessary to 

 the formation of chlorophyll in plants. Many soils are notoriously 

 deficient in iron. Only those plant cells which contain chlorophyll are 

 capable of absorbing carbon dioxide, and unless this is absorbed the 

 necessary proteids are not formed. It follows, therefore, that animals 

 feeding on plants deficient in chlorophyll cannot obtain or absorb the 

 chemical constituents necessary for health. And the moral, as far as we 

 gardeners are concerned, is : If your soil is in any degree deficient in iron 

 use basic slag or some other iron-containing manures, chlorosis in plants 



