Feb., 1895. CONTINUITY OF PROTOPLASM IN PLANTS. 109 



us, the difficulty vanishes, for we then perceive a direct channel of 

 intercommunication in the delicate threads of protoplasm which 

 traverse the wall from cell to cell, and which play a part in some 

 repects roughly comparable to that of the nerve-fibres in our own 

 bodies. 



To understand so important an alteration in our ideas as that 

 indicated above, the best plan will be to state the various steps which 

 the movement has taken since its inception. 



In 1854 Theodor Hartig (1) studied those peculiar structures, the 

 sieve-tubes, which occur in the phloem. He found here that the 

 protoplasmic bodies contained in the several elements of a tube were 

 not distinct from each other, but that each was connected with its 

 neighbour by a number of small strands of protoplasm which ran 

 through perforations in the transverse septa of the tube. This is 

 practically the first recorded instance of a connection discovered 

 between the protoplasmic bodies of neighbouring elements. 



The matter rested here for twenty-five years ; it was not until 1879 

 that Dr. Edward Tangl (2) discovered continuity in other structures 

 than sieve-tubes. He studied the endosperm cells of certain seeds, 

 and was able to demonstrate the existence of a communication between 

 the living contents of the various cells. The material he used for the 

 most part was Phoenix and Stvychnos nux-vomica. Mr. Spencer Moore, 

 a few years later, showed continuity in most of the other species of 

 Stvychnos. 



In 1882, Professor Strasburger published his famous work on the 

 cell-wall (4), and we find recorded here both a confirmation and an ex- 

 tension of Dr. Tangl's observation. It was Professor Strasburger who 

 first, in the above-mentioned monograph, called attention to the curiously 

 perforated, sieve-like membranes closing the channels of the pits in 

 the thickened cell-wall. 



In the same year a new worker came to the fore in the person of 

 Mr. Walter Gardiner (5), and it is to him more than to any other 

 single worker that we are indebted for the establishment of the im- 

 portant doctrine of continuity. So far we had only possessed 

 definite knowledge with regard to the passive reserve-cells of seeds ; 

 but Walter Gardiner turned his attention to the vitally active 

 portions of the plant, and was able to show here also a distinct 

 continuity between the protoplasmic contents of the different cells. 

 He found it to be the case in the cells of the bast-parenchyma, the 

 pulvini of leaves, the cortical tissues and the stamens of Bevbevis, 

 Not only does he give us an account of the facts observed, but he 

 also points out the significance which they possess. In the case of 

 endosperm cells, he believes we have an adaption which permits of 

 the ready transference of nutritive materials and unorganised 

 ferments from place to place ; in functionally active cells we have, 

 he thinks, channels along which stimul can be transmitted from the 

 protoplasmic mass in one part to that of another. " For instance," 



