390 



NA TURE 



{Feb. 26, 1885 



torpedo in communication with an electric battery, by 

 means of a metallic wire which connects it with the 

 port, and so cause an explosion. 



THE CONTINUITY OF THE PROTOPLASM 

 IN PLANT TISSUE 

 ^pHE translation of Dr. Schaarschmidt's paper in a 

 - 1 recent number of Nature (January 29th, 1885) gave 

 those who, like myself, are unable to read Hungarian, full 

 details both of his researches and views, and as one much 

 interested in the subject of " the continuity of the proto- 

 plasm," I should like to be allowed to make a few remarks 

 upon it. 



To refer first of all to a matter of minor importance 

 with reference to sieve-tubes, I see that Dr. Schaarschmidt 

 says : "The first direct observation was made in 1854 by 

 Hartig, and not by Sachs, as Walter Gardiner states." 

 This refers to the opening passage of my paper in the 

 Arbeiten des Botanischen Inst it tits in Wiirzburg, Band 

 III., Heft I., where I say : " A most important addition 

 was made to our knowledge of the histology of tissues in 

 1863 by Sachs, and in the following year by Hanstein, 

 when they demonstrated that in the sieve-tubes first 

 described by Hartig there are perforations in the trans- 

 verse walls, &c." I made that statement, relying, 

 as I still do, on the authority of Prof. Sachs's text-book 

 (English edition, 1882, p. 89), since it seemed to me that 

 Hartig's observation, which could not be confirmed by 

 " Mohl and others," was actually proved and demon- 

 strated beyond doubt by Sachs and Hanstein, and, 

 moreover, in fresh and not in macerated tissue. 



With respect to the main subject under immediate con- 

 sideration, I shall first make one or two general state- 

 ments as to the continuity of the protoplasm in plant 

 tissues. In my paper in the Wiirzburg Ai'beitcn, to 

 which I have already referred, I have spoken of two 

 appearances of continuity : one which I speak of as 

 direct, and the other as indirect. By direct or unbroken 

 continuity, I mean the appearance of a thick protoplasmic 

 process, extending between, and uniting the protoplasmic 

 contents of. two contiguous cells : the pits forming 

 one continuous canal, and being uninterrupted by a 

 pit-closing membrane. In this case, therefore, the idea 

 of open pits is necessitated. By indirect continuity 

 I mean the existence of a pit-closing membrane between 

 the two opposite protoplasmic processes in the pits : the 

 membrane being perforated in a sieve-like manner, and 

 thus allowing the two protoplasmic processes to be- 

 come united to one another by means of delicate proto- 

 plasmic filaments which traverse the pit-closing membrane. 

 I further stated that my observations led me to believe 

 that a pit-closing membrane was present in all cases, and 

 that the appearance of a direct unbroken continuity is 

 fallacious. (See also Roy. Soc. Proc, December 13th, 1S83.) 



Turning now to the consideration of the obser- 

 vations made upon the Florideae, I shall have to 

 differ somewhat with Dr. Schaarschmidt ; but, while 

 I do so, I wish it to be quite clearly understood 

 that I do not in the least undervalue the work of 

 those investigators to whom I refer, and who, according 

 to my view, have not actually demonstrated a continuity 

 of the protoplasm from cell to ceil, but have only observed 

 facts which render the existence of such a continuity 

 extremely probable. Thus, since I regard the perfora- 

 tion of the pit-closing membrane as proving continuity, I 

 hold that the observations of Bornet, Perceval Wright, 

 and Agardh (I have unfortunately not seen Kolderup- 

 Rosenvinge's paper) have not demonstrated continuity, 

 but have demonstrated that the pit-protoplasm clings 

 with remarkable tenacity to the pit-closing membrane. 

 Hick has simply repeated the observations of these inves- 

 tigators, and of his results the same may be said. Since, 

 therefore, Schmitz (1883) has found that a pit-closing 



membrane does exist ; that -it is perforated in a sieve-like 

 manner, and that therefore the continuity is not direct, 

 but indirect, it seems to me that to him alone belongs the 

 credit of having demonstrated the continuity of the proto- 

 plasm in the Florideae, and I have myself {Proc Camb. 

 Phil. Soc, February nth, 1884) been able to confirm his 

 results as to the existence of the closing membrane in 

 question. 



In considering the history of the subject, and leaving 

 sieve-tubes out of the question, it is clear that Tangl's 

 observation (1S80) on the endosperm cells of P/urni.r 

 and Slrychnos was the first new discovery in the direction 

 of the continuity of the protoplasm between neighbouring 

 cells. Then came Strasburger's classic work on the cell- 

 wall ("Bau und WachsthumderZellhaute," 1882) ; his ob- 

 servations on the porosity of the pit-closing membranes, 

 and his valuable suggestions as to the probability of cell- 

 wall perforation, together with the citation of instances 

 which already occurred, and his extremely interesting 

 observation with regard to the swarm-spores of Vaucheria, 

 Naturally Volvox, Pandorimi, and the zoospores of 

 Hmmatococcus offer other examples of the perforation of 

 the cell-membrane by protoplasm. 



After Strasburger came Russow. Russow read his first 

 paper at the January meeting of the Dorpat Society 

 {Sitzber. d. Dorpatct Nat. Gesell., 1882), but it did not 

 come into my hands until sometime after I had published 

 my first observation {Quart. Jour. Mic. Sci., October, 

 1882), so that, at least from that point of view, my work 

 was quite independent and original. As to the order of 

 the other papers, I agree with Dr. Schaarschmidt, except 

 that I would like to add to his list the papers of Ffurt- 

 scheller {Selbstverlag des k. k. Franz Joseph Gymnasi- 

 ums, 18S3), Will, (Bat. Zcit.,-,1, iSS4),Tangl {Sitzb. Jerk. 

 A/cad. der U'iss., Bd. 90, 1884), and Goroschankin (Bol. 

 Zeit., 41, 1883). 



As to Dr. Schaarschmidt's claiming, in l8S4,the sugges- 

 tion of the universality of the occurrence of continuity 

 of the protoplasm in plant-cells, I think that, considering 

 the state of the subject at that time (April, 18S3) some- 

 thing may also be said in my favour, for I find in my 

 Royal Society paper {Phil. Trans. Roy. Soc, April, 1883) 

 the following statement : — " Although I am aware of the 

 danger of rushing to conclusions, I cannot but remark 

 that when these results (which were foreshadowed by 

 Sachs and Hanstein, when they discovered the perforation 

 of the sieve-plate) are taken in connection with those 

 of Russow, it appears extremely probable that not only in 

 the parenchymatous cells of pulvini,in phloem parenchyma, 

 in endosperm cells, and in prosenchymatous bast fibres, 

 is continuity established from cell to cell, but that the 

 phenomenon is one of much wider, if not of universal, 

 occurrence." ' 



Passing on to the results of Dr. Schaarschmidt's second 

 paper, to which he refers, where he gives a very long list 

 of tissues in which he has demonstrated the existence of a 

 continuity of the protoplasm, I should only wish to remark 

 that while he appears to have observed in a satisfactory 

 manner, and with comparative ease, cases that have ap- 

 peared to me to be excessively difficult, yet his figures of 

 such continuity are not satisfactory, and in many of them 

 it is the direct and not the indirect continuity which his 

 drawings represent. As I have stated elsewhere (Arb. d. 

 Pot. Inst. Wiirzburg) an examination of fresh unswollen 

 tissue with iodine and chlor. zinc. iod. will always demon- 

 strate the presence of a pit-closing membrane. 



I now come to a subject which I approach with some 

 regret, since, in dealing with it, I have to dissent from the 

 expressed opinions of a number of competent observers, 

 and especially do I feel this regret with regard to one of 

 those papers — viz. that by one of the most distinguished 



1 Mr. Dyer has already very kindly alluded to this subject on my behalf. 

 It will be observed from the text that at that time (April, 1883), owing to the 

 hurry of publication I had not referred to Hartig's paper (February 18, 1885). 



