74 



NA TURE 



[August 26, 1922 



marine radio-telegraphist. Detailed instructions are 

 given as to the methods of adjusting the various 

 standard Marconi sets. Descriptions are also given 

 of the apparatus of the Telefunken and Radio-Com- 

 munication Co. The diagrams are very clear and the 

 tables, rules, instructions, etc., included have been well 

 selected. 



(3) As the bulk of the world's radio-communication 

 is carried on by continuous wave (C.W.) systems, 

 it is natural that there should be a demand for element- 

 ary but accurate descriptions of these systems. The 

 number of C.W. arc stations now exceeds a thousand, 

 and more than 10,000 kilowatts have been installed 

 for their operation. There are also many high 

 frequency and valve generator stations. As space 

 is limited in this booklet, some of the descriptions of 

 important methods are too brief to be of much help 

 to the reader, and there are notable omissions. The 

 chapters on the advance of the C.W. system and on 

 the Poulsen arc are instructive and contain novel 

 matter. We can commend the book. 



Plant Morphology and Physiology. 



Practical Plant Biology : A Course of Elementary Lec- 

 tures on the General Morphology and Physiology of 

 Plants. By Prof. H. H. Dixon. Pp. xi + 291. 

 (London : Longmans, Green and Co., 1922.) 6s. 



A TEXT-BOOK by such an experienced teacher 

 as Prof. H. H. Dixon is very welcome. To 

 judge from the introduction, this book represents in 

 condensed form the series of lectures which the author 

 has found most suitable for the introduction of his 

 subject to a class in which medical students predom- 

 inate. At the end of each lecture brief notes are added 

 as to the scope of the practical work to be carried out in 

 conjunction with the course. Each lecture occupies on 

 the average about eight pages, and in the thirty lectures 

 a wide series of types are covered, from unicellular forms 

 to the flowering plant. Considerable physiological 

 work is included, and the subjects of nuclear division, 

 heredity, and evolution occupy the last three lectures. 

 The treatment is therefore of necessity much condensed, 

 and an elementary student would find it difficult to 

 use the book except under guidance. 



Three salient features in the book have impressed 

 the present reviewer. The first is the interest and 

 charm with which the author's style and personality 

 invests the subjects of the elementary course. It is 

 clear that each time Prof. Dixon renews his acquaint- 

 ance with these familiar plants, his class will find him 

 filled with the enthusiasm of a first encounter. The 

 student cannot forget .that he is studying living plants, 

 NO. 2756, VOL. I io] 



even when examined in the remote region of a " micro- 

 scopic field." With the aid of a " ghost micrometer," 

 an instrument Prof. Dixon demonstrated to Section K 

 of the British Association for the Advancement of 

 Science at Edinburgh last year, comparative data as 

 to size, rate of movement, etc., are always kept before 

 the student. The brief instructions given on p. 74 for 

 practical work with Spirogyra provide an excellent 

 example of how to make a student realise that Spiro- 

 gyra is a living object in a three-dimensional world, 

 and not a design transferred from the plane of the 

 microscopic image to the plane of the paper. The 

 second striking point is that the author has found it 

 advisable to build up a knowledge of the plant by 

 progress from the simpler unicellular forms to the more 

 complex vascular plants. The initial difficulty of the 

 unfamiliarity of the plant forms thus first introduced 

 to the student is grappled with most successfully, and 

 very interesting use is made of the opportunity thus 

 provided, at an early stage of the course, of indicating 

 the great practical and human significance of biological 

 studies. On the other hand, this method of approach 

 appears to make the treatment of plant physiology 

 more disconnected and less experimental. Photo- 

 synthesis appears fairly early in the course, but the 

 experimental treatment at this stage does not en- 

 courage any effort to associate the process with gain 

 in dry weight and in carbon content. Respiration is 

 discussed first as an anaerobic process with yeast, and 

 later is treated more generally under Chlamydomonas. 

 While some general questions as to the water relations 

 of the cell appear in Lecture II., root pressure and 

 translocation, hinted at in Lecture XIX. on the fern, 

 are not fully treated until Lecture XXV. 



Coming to the third point of interest, as might be 

 anticipated from the author, a much wider use is 

 made of relatively complex data from physics and 

 chemistry than is usual in an elementary botanical 

 text-book. If botany is to progress this seems to be 

 an essential development, even if it implies ultimately 

 a recognition that elementary botany courses need 

 building upon the physics and chemistry of the final 

 years of the graduate science course ! Lecture II. 

 introduces us to diffusion and osmosis, Lecture III. to 

 phenomena of the colloid state, Lecture IV. to enzyme 

 action and surface phenomena in heterogeneous sys- 

 tems. This pace is rather sweeping and makes great 

 demands upon the student. It is probably also in- 

 evitable that as botanists venture into these paths, the 

 pioneers will stumble occasionally in their unfamiliar 

 surroundings. The attempt to define the difference 

 between a gel and a sol on p. 22 appears to be a case 

 in point. The explanation here given of the structure 

 of a gel would render the phenomena of diffusion in 



