November. 1912. 



KNOWLEDGE. 



443 



a general view of the range of his scientific knowledge. Such 

 an epitome as Dr. Lones now gives us is a great help to the 

 student, and 1 think it will be welcomed by all naturalists and 

 physicists who care for the historic aspect of their science. 

 In such an epitome one loses much; one misses Aristotle's 

 homely style of narrative and all the archaic terms of his 

 phraseology, which even a translation does not let us wholly 

 lose. There is a certain charm in the discursiveness of his 

 style, in which one seems to trace how his mind caught up 

 point after point, and where every here and there some great 

 and original thought looms out amid the simpler narrative. 

 But the epitome serves a good and even indispensable purpose 

 of its own. and in this case it seems to have been made with 

 skill and learning, and with loving sympathy for the work of 

 the philosopher. 



In an introductory chapter the writer gives us a brief and 

 pleasant account of Aristotle's life, of his various writings and 

 of the history of .Aristotelianism. He reminds us, for instance, 

 that the phrase " there is nothing new under the sun " was an 

 old saying in .'\ristotle's day, and was a favourite of Aristotle's 

 own. He sketches some of the many ideas, or some of the 

 many words, that come to us direct from Aristotle ; he shows 

 us. for instance, that in such familiar words as form and 

 habit, faculty and energy, essence and ([uintessence, we are 

 using .Xristotle's language ; that diptera and coleoptera and 

 selachia .and cetacea are .Aristotle's own words ; that the 

 physicist, the naturalist and the metaphysician are, ipso 

 nomine, .Aristotelians. 



The book proceeds in the next place to give us an account 

 of .Aristotle's physical writings, such as are contained in his 

 work on Meteorology and in his tract on the Heavens ; and 

 then, in greater part, it consists of an orderly account of 

 •Aristotle's Natural History, as gleaned from the various 

 biological treatises. In the beginning of this latter portion of 

 the book we find an account of .Aristotle's discussion concern- 

 ing the relation between animals, plants, and things inanimate, 

 the various forms or grades of the " Vital principle " : in short, 

 the question of the passage from lifeless to living matter, 

 which is to-day as open to discussion as ever, and can scarcely 

 be discussed at all without reference to .Aristotle's own terms 

 and arguments. From the manner of composition of the 

 elements, fire, water, earth and air, we are led on to the tissues 

 and organs of the body, the description of which leads off into 

 many interesting bye-ways of physiology and anatomy. And 

 lastly, after brief chapters on animal locomotion and on 

 generation and development, the book ends with an account of 

 .Aristotle's classification of animals — that is to say, of his 

 knowledge of systematic zoology. 



Dr. Lones' book is too close-packed to be easy reading : it 

 does not set forth to be a contribution to Aristotelian criticism, 

 and here and there there are minor points of interpretation 

 with which we are not inclined to agree. Hut be all this as 

 it may, the book is meant to be useful, and it seems to me to 

 make good its claim to usefulness. It is plain that the writing 

 of it has been a labour of love and the work of years. 



D. \V. T. 



HORTICULTURE. 



Present-day Gardening. — Chrysanthemums. — By Thomas 

 Stevenson, with Chapters by C. H.\rman Payne and 

 Charles E. Shea. 112 pages. The Rock Garden. — By 

 Reginald Parker, lis pages. Tulips. — By The Rev. 

 J. Jacoh. 116 pages. Each with 8 coloured plates. 

 8J-in. X 6i-in. 



IT. C. i E. C. Jack. Price 1/6 net. each.) 



The three books whose titles are given above belong to a 

 series which is being edited by Mr. R. Hooper Pearson, the 

 Managing Editor of The Gdrdeners' Chronicle. The special 

 feature of these useful volumes is that they are all written by 

 experts, and that they are each illustrated with eight coloured 

 plates reproduced from photographs by .Mr. T. Ernest 

 Waltham. Verj- many of these are strikingly beautiful, and 



they are the best pictures of their kind that have been 

 produced for the purpose, while, when it is noticed that 

 the price of the books is only Is. 6d. each, it will be obvious 

 that all lovers of flowers are to be congratulated on having 

 many of the best varieties put before them as they appear in 

 flower in addition to just the kind of information they recjuire. 

 The pictures of chrysanthemums may be specially mentioned, 

 though the views in " The Rock Garden " are not quite so 

 pleasing as the individual plants, probably owing to their 

 backgrounds, though they give a good idea of the appearance 

 of forms illustrated. Fifteen of the books have appeared and 

 a number of others are in preparation. ... . , ... 



.MYCOLOC.V. 



FiDijioid Diseases of .Agricultural Plants. — By Jakob 



Kkiksson, Fil.Dr. 208 pages. 117 illustrations. 



8i-in. X 5A-in. 



(Bailliere, Tindall & Cox. Price 7 6 net.) 



The name of Professor Eriksson is a sufficient guarantee for 

 the excellence of this text-book on the diseases of plants 

 caused by fungi. On turning to the account of the rust-fungi 

 (Uredincae), on which Professor Eriksson has published so 

 extensively, one naturally finds a statement of the author's 

 "mycoplasm" theory. These fungi have a somewhat complex 

 life history, in the course of which several different kinds of 

 reproductive cells are produced in succession, and until about 

 ten years ago it was generally supposed that the infection of 

 plants in spring or early summer was invariably due to the 

 germination of spores which had passed the winter in a resting 

 state. According to Eriksson, however, this explanation is 

 insufficient to account for the spread of certain rust-fungi, and 

 he claims to have discovered that the fungus can and does 

 exist in the cells of the " host" plant as "a formless plasma 

 body, a sort of plasiiiodiuni. symbiotically fused with the 

 protoplasm of the cells, and forming together with these a 

 mycoplasm" (to (|Uote from the present work). "The 

 mycoplasm-carrying cell presents otherwise a normal appear- 

 ance, with nucleus, chlorophyl bodies, and so forth. There 

 cannot be recorded any parasitical fungoid life that would 

 waste away the host plant. We may surmise that the 

 fungus in this way can exist in most of the chlorophyll- 

 carrying cells, up to the ears and bloom, in all sorts of seed 

 that are specially suitable for the fungus, or, as it is express'-d, 

 are in a higher degree susceptible. The period during which 

 the fungus exists in this latent state varies in different cases. 

 From four to five weeks it might last for as many months and 

 even for some years. This is the dormant stage of the 

 mycoplasm. Sooner or later, at a certain period of the life of 

 the host plant, at a certain season, and with favourable 

 environment of circumstances Isoil. moisture, warmth, light, 

 and so forth) for the development of the fungus, and varying 

 with different sorts of rust, there will commence a new stage 

 in the existence of the mycoplasm — the stage of maturing, 

 when the fungus forces its way out from the symbiotic complex, 

 penetrates the walls of the cell, and develops an intercellular 

 mycehum. This maturing seems to be of short duration : it 

 lasts only for a day or two. or possibly only some hours. As 

 soon as the intercellular mycelium begins to form, it takes 

 generally one week before open rust sores with spore-stuff 

 begin to appear on the surface of the plant." It is only 

 necessary to add that this remarkable explanation has received 

 very little support from other investigators, to say nothing of 

 its inherent improbability on general grounds. One cannot 

 blame an author of a text-book for giving prominence to his 

 own theories, but in this ca.se some of the evidence against 

 the mycoplasm theory might have been added, if only in a 

 foot-note, for the guidance of students. 



It is a pity this English version of Eriksson's book was not 

 read through by a competent botanist in this country before 

 publication. Had this been done, the English rendering would 

 doubtless have been more elegant if less clingingly exact in 

 its fidelity to the original, and we should not have met such 



