660 



SCIENCE. 



[N. S. Vol. XV. No. 382. 



Java, are continued throughout a number of the 

 easterly islands: also that in deep water and 

 distant from shore, land remains such as 

 fruit and leaves of palms are found in dredg- 

 ings, confirming from this region the obser- 

 vations of Alexander Agassiz on the Blahe. 

 Bashford Dean. 



Die Beizleitung und reizleitenden Strukturen 

 hei den Pflanzen. By B. Kemec. Jena, 

 G. Fisher. 1901. Pp. 153; pi. 2. Price, 

 Mk. 7. 



Nov^adays it is to be expected that any 

 theory developed in connection with the phe- 

 nomena of animal life will quickly be applied 

 to investigation in the action of plants and vice 

 versa. Witness the well-known exploitation 

 of heliotropic phenomena in animals after 

 their elaboration in plants. Since the dis- 

 covery of the fibrillar structure in the nervous 

 system of animals and the development of the 

 neuron theory have shed so much light upon 

 the propagation of impulses in animals, it 

 was to be expected that similar investigations 

 should be made upon plants. This has been 

 done by Nemec and the results are embodied 

 in a book of considerable size. 



Though he gave some attention to geotropic 

 and other stimuli, Nemec studied chiefly the 

 propagation of the stimulus caused by wound- 

 ing, because this manifests itself by a notable 

 disturbance in the structure of the cell. The 

 protoplasm of cells adjacent to the wound 

 aggregates upon the side of the cell next to 

 it, whither also the nucleus migrates. This 

 disturbance spreads in all directions at a defi- 

 nite rate (in the root of onion about 1.25 mm. 

 lengthwise in the first fifteen minutes), and 

 recovery follows shortly. The propagation is 

 most rapid in the longitudinal axis. Nemec 

 sought a structural basis for this difference 

 and believes that he has found it in proto- 

 plasmic strands or fibrils, which are readily 

 demonstrable in certain cells, particularly 

 those of the plerome. These strands run 

 lengthwise from one end of the cell to the 

 other and are resolvable, with proper staining 

 and magnification, into fibrils, each of which 

 is surrounded by a distinct sheath. In the 

 center of the cell the strands are often large 



and distinct, but near the ends they spread 

 out into a brush of fibrils, which reach the 

 wall but do not penetrate it. According to 

 Nemec, propagation of the impulse takes place 

 along these fibrils, becoming general and dif- 

 fuse in the protoplasm at the ends of the cells, 

 and passing from one cell to another by way 

 of the minute general protoplasmic connec- 

 tions, which by analogy he assumes to exist, 

 though he does not demonstrate them. Nemec 

 lays much stress upon the fact that in adjacent 

 cells the fibrils correspond on opposite faces of 

 the wall, though the significance of this point 

 is not clear in view of the lack of demon- 

 strable connection through the wall. Such 

 fibrillar structures were found in several mon- 

 ocotyles, dicotyles and some ferns. Inas- 

 much as operations for the removal of the 

 fibrils alone were impossible, Nemec caused 

 their degeneration by sudden changes of tem- 

 perature, finding afterwards the rate of prop- 

 agation retarded. In roots of Vicia Faha, 

 where fibrils are found only in the plerome, 

 the severance of the plerome inhibited geo- 

 tropic curvature entirely or at least above the 

 cut, the inference being that it did so by 

 interruption of the fibrils. 



The work of Nemec is certainly a careful 

 and thorough piece of research, which will 

 doubtless stimulate further inquiry along this 

 line. It is not convincing, however, in its 

 present stage. The author himself admits 

 that impulses are transmitted by cells in which 

 there are no fibrils, holding only that when 

 present they facilitate propagation. If this 

 be true they should be best developed in those 

 organs whose reactions are quickest. Yet 

 Haberlandt — who has already interested him- 

 self in the problem — ^has been unable to dis- 

 cover them in the vicinity of the sensitive 

 hairs of Aldrovandia, the stamens of Opuntia, 

 or the tendrils of Cucurhita. Further, it 

 should be noted that the cell rows in which 

 the fibrils are best developed — often those 

 which become trachoee — are not only an un- 

 likely line of transmission but that no actual 

 protoplasmic connection in them has been 

 shown. Finally, the experiments showing re- 

 tardation following interruption or disorgan- 

 ization of the fibrils are inconclusive because 



