May 26, 1898] 



NATURE 



75 



differentiation of indifferent rudiments and that of the 

 iietamorphosis of rudiments materially differing from 

 >ne another. Dr. Goebel shows a strong bias in favour 

 of the latter. Thus he says a foliage leaf is not a foliage 

 leaf in the later stages of its development only, but the 

 naterial constitution of its rudiment determines its 

 levelopment. Internal or external influences may, how- 

 \er, direct this development along other lines. To 

 lustrate this point of view he describes the metamor- 

 phosis of the rudiment of a foliage leaf of a maple into a 

 scale-leaf. But it must be confessed that although his 

 arguments and illustrations are interesting, he fails to 

 convince the reader that there are less difficulties in the 

 way of the theory of metamorphosis, involving as it does 

 some form of evolution in ontogeny, than are presented 

 to the theory of differentiation, which in this case appears 

 to be based on epigenesis. The indisputably indifferent 

 nature of the cells forming the archesporial tissues and 

 those in other positions in leaves, which are able to give 

 rise to adventitious buds, are arguments in favour of the 

 indifferent nature of all the leaf-cells, even in compar- 

 atively late stages of development. That no absolute 

 material difference exists between the rudiments of 

 different categories of organs is rendered probable by the 

 absence of any definite demarcation between stem and 

 leaf, as is shown by the example of Utricularia, which 

 Dr. Goebel himself has investigated. Indeed in this 

 direction Dr. Goebel goes further than the majority in 

 maintaining that the vegetative body of Lemna is com- 

 posed of branching leaves, and is not a leafless stem. 



The purely morphological view, without regard to the 

 functions of the organs considered, may often lead to 

 misconception, and Dr. Goebel takes hairs as an example 

 of this possibility. Thus according to him no sensible 

 man would call a fern sporangium a " trichome " ; for 

 one cannot believe that either in the life-history of the 

 individual, or of the race, that a sporangium arose by 

 the metamorphosis of a hair. And yet the belief, which 

 Dr. Goebel himself seems to share, that a stamen is a 

 metamorphosed foliage leaf appears to rest on similar 

 grounds, especially when viewed in the light of Bower's 

 researches on spore-producing members. 



Of great interest are those sections of the book dealing 

 with the symmetry of organs and with the effect of light 

 on dorsi-ventrality. The author finds that Selaginella 

 sanguinoletita possesses leaves of two kinds, and is dorsi- 

 ventral when subject to bright illumination ; while if it is 

 exposed to feeble light, it possesses leaves of one kind 

 only and is radially symmetrical. The arrangement 

 which is induced by the situation of the individual of this 

 species, occurs normally on different parts of the same 

 individual of other species. In these the individual is 

 radially symmetrical in the lower portions of the stem, 

 while the upper parts are anisophyllous. Furthermore, 

 Dr. Goebel has been able to cause S. helvetica^ which is 

 normally anisophyllous, to considerably lessen the contrast 

 between the two kinds of leaves by simple etiolation. 

 Thus it appears that in some the adaptation is onto- 

 genetic in its nature, and is brought about by the actual 

 circumstances of the individual ; in others it is inherited, 

 and not materially affected by the immediate surround- 

 ings, although probably brought about by the relations of 

 a succession of individuals to light. 

 NO. 1 49 1, VOL. 58] 



In the succeeding section, on the difference between 

 the structures of organs in the adult and early stages of 

 development, there is much of interest, Polysiphonia 

 Bendert, one of the most remarkable examples of this 

 difference, has been already described by Dr. Goebel. In 

 this alga the first stage resembles the adult in possessing 

 a cylindrical thallus. This gives rise to one or more flat 

 structures, which apply themselves to the surface of other 

 algas, and which are wholly different from both the first 

 and final stages in appearance. Only before the form- 

 ation of the reproductive organs are the adult cylindrical 

 branches developed. 



Passing on to the development of the higher plants, 

 perhaps every one will not agree with the author in his 

 view that the simpler form of the primary leaves of 

 seedlings is due to an arrest of development. The 

 existence of a more complicated form in some primary 

 leaves than in those of the adult stages, must make one 

 hesitate before accepting the theory of arrested develop- 

 ment in every case, and may suggest that a similar reason 

 for the difference between the leaves of the seedling and 

 those of the adult exists both when the former are more 

 simple and when they are more complex than those of 

 the latter. 



The section on vegetable teratology may be noted, as 

 in it Dr. Goebel gives his support to Beyrinck's extension 

 of Sachs' hypothesis, that the difference in form of plant 

 organs is due to a difference of substance, and that 

 changes in form are referable to alterations in the 

 nutrition of the parts involved. Beyrinck's view is that 

 galls are caused by such an alteration in the nutrition of 

 the part in response to the stimulation by the gall- 

 producing animal. 



The last part of the book is devoted to a discussion of 

 the influence of correlation and external stimuli on the 

 form of plants. It is not behind the earlier parts in 

 interest and wealth of example. Among the more 

 important matters touched upon in this part are Linde- 

 muth's experiments on the production of seeds in bulbous 

 plants, Sachs' investigations on the relation of flower- 

 production to light, and Lothelier's observations on the 

 conversion of the spinous leaves of Ulex into flattened 

 forms, in a moist atmosphere. Dr. Goebel doubts that 

 this modification of spines due to moisture is of frequent 

 occurrence, and believes that Lothelier observed isolated 

 examples. 



With confidence Dr. Goebel's book may be recom- 

 mended to all who are interested in theoretical botany. 

 It is full of suggestion and novelty, and its occasionally 

 dogmatic style in no way lessens its tendency to arouse 

 interest and discussion, H, H, D, 



A GREAT NORTH ROAD. 

 A Northern Highway of the Tzar. By Aubyn Trevor- 

 Battye, Pp. xiv -f- 256. (London : Archibald Con- 

 stable and Co., 1898.) 



MR. TREVOR-BATTYE gives in this book a very 

 interesting account of his journey home from 

 Kolguev, an island in the Arctic Ocean, on which he was 

 for some time ice-bound. 

 The journey was undertaken in October, a time known 



