with special Reference to the Mode of Connexion of Cells. 107 



is curiously limited and hardly extends beyond the immediate neigh- 

 bourhood of the absorbent foot of the young embryo. The mode of 

 disappearance of the wall by the coarse corrosive action of the 

 ferment, and the manner of its proceeding with so little relation to 

 the threads, seems to indicate that the structure of endosperm cells 

 has more relation to the conduction of impulses and of food supply 

 than to the needs of germination. 



Satisfactory as are the results derived from the study of endo- 

 sperm cells, the real success was achieved when the method was so 

 modified that it could be applied with certainty and success to the 

 investigation of ordinary tissue, and to specialised forms of it, such 

 as pulvini and tendrils. 



The unsatisfactory character of the somewhat meagre results 

 hitherto obtainable have not, I think, succeeded in generally estab- 

 lishing a conviction that the structures postulated have necessarily 

 an actual existence. Botanists have, on the contrary, been inclined 

 to look askance at results depending upon such statements as "a 

 stained area" or "a doubtful striation," and there lurked in the 

 minds of many, the suspicion that the histology of endosperms was 

 possibly exceptional, and peculiar to that tissue. 



For the future such doubts need no longer be entertained, since 

 it is now easy to demonstrate that the structure exhibited by 

 endosperm tissue is in all respects entirely typical of plant tissue 

 generally. 



In these days of active investigation, it is not often given to one to 

 be the medium for the criticism of his own research. This good 

 fortune, however, now falls to me, and I hasten to say that in the 

 light of the present investigation it is quite clear that apart from 

 endosperms, and with such exceptions as Aucuba jajponica, my earlier 

 work on the continuity of the protoplasm, in pulvini and other 

 tissues, does not affc'ord absolute proof that a communication between 

 cells actually occurs, but for the most part only brings forward 

 strong evidence that such connection is exceedingly probable. At 

 this juncture, also, I note, with satisfaction, that the results then 

 obtained were able to save me from the error of a belief in the 

 existence of a system of open pits which have since then been 

 repeatedly figured and desciibed, and against which I have persist- 

 ently spoken. 



As I have already remarked, my new method makes it possible to 

 establish with certainty that the structure of all kinds of plant 

 tissue is precisely similar to that of endosperms, and that exactly 

 the same modifications are exhibited. In pitted cells every pit- 

 closing-membrane is traversed by its group of threads, and in un- 

 pitted cells similar groups also occur. In square-ended tubular cells, 

 such as those of ttie leaf stalk of Ldium martagon (fig. 4), the 



