372 



NA TURE 



[August 15, 1901 



nervous system of animals ; and the transmission of the 

 stimulus has commonly been referred either to a serially 

 altered condition of the protoplasm in its relation to 

 water, or to vague suggestions arising from the well- 

 known facts of protoplasmic continuity between adjacent 

 cells, the onus of transmission being cast on the proto- 

 plasm as a whole. 



Dr. NSmec, however, contends that these notions 

 demand reconsideration, and he gives an account in the 

 book before us of observations which, if confirmed by 

 subsequent examination, are of great importance as 

 enabling us to obtain a more definite comprehension of 

 the relations existing between perception and reaction in 

 the motile organs of plants. 



The author begins by studying the effects on the 

 protoplasm of wounding the sensitive regions of roots 

 and other organs, and, in the main, he confirms, and at 

 the same time extends, the conclusions arrived at by 

 Tangl some years ago. He distinguishes two traumatic 

 phases as consequent on such an operation. The first, or 

 primary, response consists in an aggregation of the proto- 

 plasm, and it may be of the nucleus also, to the wound- 

 ward end of the cell. This effect is propagated with 

 diminishing rapidity in a direction away from the wound, 

 and at a rate which is not equal for the different tissues 

 composing the organ. A curious fact relating to the 

 travelling onward of the effect is brought to light in 

 connection with cells in which nuclear division is pro- 

 ceeding, for the disturbance appears to miss these cells, 

 though it reappears immediately beyond them. Shortly 

 after this primary manifestation has passed over a cell, 

 recovery supervenes, only, however, to give place to a 

 secondary phenomenon. The protoplasm of the cells in 

 the vicinity of the wound assumes a more or less gela- 

 tinous character, and the vacuoles begin to undergo 

 fusion. This secondary effect is, however, apparently 

 rather local, and t ravels neither so far nor so fast as 

 does the primary one. It may perhaps be questioned 

 whether the latter is not, at least mainly, due to a dis- 

 turbance of hydrostatic equilibrium in the cells conse- 

 quent on the lesion of the organ, whilst the secondary 

 change may possibly be associated with the febrile 

 condition kno wn to be induced by mechanical and other 

 injuries. Further investigation of the phenomena by 

 means, e.g., of plasmolysing reagents might prove of 

 interest. 



Of more general importance than these results is the 

 statement that the author has succeeded, by means of 

 appropriate stains, in demonstrating a continuous fibrillar 

 structure in the cytoplasm. These fibrilte, which are 

 figured as so mewhat thick cords, traverse the cell chiefly 

 in the longitudinal direction ; and, although the point 

 was not definitely settled, they appeared to connect with 

 similar ones in the contiguous cells of a longitudinal 

 series. They are not equally present in every kind of 

 tissue, sometimes they occur in the cortex whilst in other 

 cases they are most abundant in the plerome. They are 

 almost always met with in sensitive and motile organs, 

 to which also they appear to be almost exclusively con- 

 fined, and Nemec believes that they represent the means 

 whereby stimuli are rendered transmissible. He finds 

 that conditions which impair or abolish such transmission 

 also affect the fibrillar structure. The latter may, indeed, 

 NO. 1659, VOL. 64] 



be temporarily or permanently disorganised, and so long 

 as this is the case the organ appears to be insensitive. 



Nemec himself considers some of the objections which 

 may be urged against his view of the functions of the 

 fibrils. Thus it might be argued that the same causes 

 which result in a dislocation of the sensitive mechanism 

 of an organ may also, and concomitantly, destroy the 

 normal structural configuration of the protoplasm, but 

 that it does not therefore follow that the two should 

 necessarily stand in any causal connection with each 

 other. The force of such an objection is, however, 

 weakened by two observations made on roots. In Viiia, 

 the fibrils are restricted to the axile cylinder (plerome) of 

 the root. Now if the cortex be severed by an annular 

 cut, after the disturbance which ensues as the result of 

 the injury has passed away,''the organ recovers the power 

 of perceiving and transmitting stimuli ; if, however, the 

 plerome be cut through, by means of a needle, then the 

 power of future response in the case of stimuli affecting the 

 distal end will be found to have been finally lost. Again, 

 it is known that the!perception, by roots, of the stimulus 

 given by gravity is limited to the actual growing point, 

 whilst the motile region, in which the stimulus provokes a 

 visible result, is situated at some distance behind it. If 

 the tip of the root be cut away, the power of further 

 response to the gravity-stimulus is thenceforth in abeyance 

 pending the regeneration of the apex. Now in some 

 instances it was observed that the power of response to 

 the stimulus was not recovered even after the formation 

 of the new growing point, but in every one of these 

 cases further examination showed that the fibrillar con- 

 tinuity had not been properly restored. Hence the path 

 of transmission between the percipient apex and the 

 executive motile portion of the root still remained 

 interrupted. 



It is clear that Dr. Nemec has opened up a promising 

 field of investigation, and one which is no less important 

 from the point of view of the plant world than fiom that 

 of the lower animal organisms in which also no permanent 

 nervous system is present. It is to be hoped that the 

 observations may be thoroughly tested by physiological 

 as well as by histological methods, a task which should 

 be rendered the easier inasmuch as the structures can 

 apparently be identified in the still living cells. 



J. B. F. 



AMERICAN AGRICULTURAL RESEARCHES. 

 Yearbook of the United States Department of Agricul- 

 ture, 1900. Pp. 888. (Washington, D.C., 1901.) 

 THE bulky volume before us is as full of interest as 

 its predecessors, and as profusely illustrated. Its 

 contents are extremely various, for, as mentioned in the 

 preface, there is not a single bureau, division or office of 

 the Department that has not contributed to the present 

 book. The reports occupy 633 pages. These are 

 followed by an appendix of 231 pages, in which a great 

 deal of statistical and miscellaneous information is 

 brought together for the use of the farming community. 

 We can only refer to a very few of the subjects discussed. 

 The report on the cultivation of Smyrna figs in 

 California is full of interest of many kinds. For this fig 

 to be brought to perfection, it is necessary that the 



