NATURE 



561 



THURSDAY, OCTOBER 3, 1907. 



PROBLEMS OF ANCESTRY. 

 Vorlrii^^e itbcr bolaiiiscl'.c Stammcs^i;t'schichic, 

 gchalten an der Reichsuniversitdt zu Leiden. Ein 

 Lclirbuch der Pflanzensystematik. By J. P. Lotsy. 

 ^'ol. i., Algen und Pilze. Pp. iv + 828. (Jena: 

 Gustav Fischer, 1907.) Price 20 marks. 



THE motive inspiring the production of this im- 

 portant work is indicated on the title-page in 

 the " motto " quoted from Coulter: — 



" The most difficult as well as most fascinating 

 problem in connection with any group is its phylo- 

 geny. The data upon which we base opinions con- 

 cerning phylogeny are never sufficient, but such 

 opinions usually stimulate research, and are necessary 

 to progress." 



Its pages show how stimulating the inquiry has been 

 to the author, and we have seldom met with a book 

 more likely to awaken inquiry in its readers or to 

 suggest further research. Very different values may 

 be placed on the conclusions as to the phylogeny of 

 several of the groups, and on the characters regarded 

 as of chief importance in forming the system of classi- 

 fication, and further information on many points is 

 very desirable ; but there can be only one opinion as 

 to the manner in which the information is conveyed 

 to the reader. Under each group is an admirablv 

 clear and full, yet concise, statement of the investi- 

 gations that have been made upon it, and of their 

 results, while an extensive classified bibliography 

 refers the student to the original and full sources of 

 information. Numerous illustrations, original or 

 .-ifter those of the best monographs, add greatly to 

 the usefulness of the work, and to its worth as an 

 exponent of the most recent researches into the struc- 

 ture and cytology of the alg» and fungi. 



The form of the book appears somewhat artificial, 

 its substance being divided into thirty Vorlesungcn 

 of very unequal length, e.g. that on Exoascineae 

 (xxvi.) of four pages, and that on Basidiomycetes 

 (XXX.) of eighty-eight pages. As these could scarcely 

 have each been the subject of a single lecture, and as 

 the longer Vorlesungen in some cases include 

 several groups, this arrangement does not appear so 

 convenient as the more usual division into chapters 

 and sections. 



The course of lectures opens with the discussion of 

 what constitutes a living being, and of the agree- 

 ments and differences between plants and animals, 

 but very soon passes to the consideration of the 

 simplest organisms as individual "energids," the 

 multiplication of these, and the bodies built up of the 

 combinations of" energids." An outline of the scheme 

 of classification given early in the first lecture derives 

 all plants from Protomastigina, and traces the sup- 

 posed derivation of the several groups from these 

 early forms, and their relations with one another. 

 The system of classification of the green algae is 

 stated by Dr. Lotsy to be largely based on that set 

 forth by Blackman and Tansley in 1902 in the " New 

 Phytt>logist." Great importance is attached to the 

 number and arrangement of the cilia borne by the re- 

 NO. 1979, VOL. 76] 



productive cells, or at least by the male gamete; 

 and these characters are employed in tracing the 

 relationships between widely different groups, e.g. 

 the Isokontae are regarded as representing the ances- 

 tral condition of the Pteridophyles and seed-plants. 



Scarcely less importance is given to the studv of 

 the "energids," or very simple units of individual life, 

 the progress being traced from the monoergid to the 

 polyergid organisation within the larger groups, with 

 resultant advance in complexity of structure. That 

 the conception is one of much value in stimulating 

 inquiry cannot be disputed, but it may be questioned 

 whether it is not carried too far in practically identi- 

 fying the energid with the nucleus. The very dif- 

 ferent behaviour of the nuclei of the reproductive cells 

 within a single family, and even within a single 

 genus at times, especially among fungi, may well 

 suggest the need of caution in such matters. 



It is stated in the preface that the plan of the work 

 was resolved on after perusal of a lecture by Dr. 

 Hugo de Vries, in which a higher plant is regarded 

 as a double organism. Dr. Lotsy was led to en- 

 deavour to trace out in theory how the return to the 

 stage of a single organism is effected, and thus 

 arrived at the conception of the two generations 

 denoted as x and 2x. The book before us embodies 

 the effort to determine the extent of each of these 

 generations, and in which groups of Thallophyta it is 

 possible to detect them, the essential distinction be- 

 tween them being the well-known reduction in the 

 number of chromosomes in the nuclei of the one 

 generation to one-half those of the other. With this 

 as a clue. Dr. Lotsy seeks to determine the relations 

 of gametophyte and sporophyte in the Thallophyta, 

 extending to these the conception of the alternation of 

 generations so familiar in its applications to the 

 .Vrchegoniatae. He shows a remarkable familiarity 

 with the results of the most recent as well as of the 

 classical researches into the structure and reproduc- 

 tion of the various families, and applies his lead- 

 ing ideas in a very consistent and able manner. We 

 think that the known is still too limited to permit 

 of a secure foundation being laid for the universal 

 employment of such a criterion ; but such a theory, 

 applied with the author's thoroughness and width of 

 view, must stimulate further investigation, and thus 

 do excellent service in the study of botany. The 

 doubts that must be felt with regard to the validity 

 of some of the assumptions and conclusions will 

 themselves lead to inquiries that must advance know- 

 ledge still more effectively. Several very important 

 discussions of wide interest are introduced in relation 

 to certain groups that illustrate them, e.g. that on 

 the asexual cells and the gametes in Chlamydomonas 

 leads to the consideration of the part taken by the 

 nuclei in inheritance and artificial development of 

 the egi^ under the stimulus of inorganic salts in solu- 

 tions. \'olvox gives further occasion of discussion 

 on heredity, as does also Hydrodictyon, in which the 

 effects of sugar and other substances on the methods 

 of reproduction receive notice, and the relations of 

 the X and 2X generations are compared with what 

 occurs in Uredineae. Illustrations of similar kind are 

 introduced from among animals also. The functions 



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