100 PROTOPLASMIC CONTINUITY IN THE FUCACE^. 



remain uncontracted at the ends. Hence, in the cortical layers 

 and in the filaments of the central tissue the protoplasm appears, 

 under a half or quarter inch objective, to run uninterruptedly from 

 cell to cell in the longitudinal direction. PL 255, Fig. 2. 



Similar phenomena are met with in the lateral diverticula 

 which unite the filaments and cortical layers transversely, the 

 protoplasm ajypccuiiKi to run across without a break. 



The fibres too, which are interwoven with the central filaments, 

 seem to have their contents continuous from one end to the other. 



A mere suspicion of continuity, however, is not sufficient to 

 satisfy the demands of scientific logic, and to be convinced that it 

 actually exists the state of affairs at the ends of the cells must be 

 more closely investigated. For this purpose sections prepared by 

 the third method described above must be made use of, and even 

 these must be supplemented by others of a still more demon- 

 strative character. The latter may be obtained by slightly 

 modifying the modes of treatment as follows : — 



1st. Sections that are to be treated by the second method 

 should be previously placed for a few moments in a weak solution 

 of ordinary bleaching powder. 



2nd. Sections that have been treated by the third method 

 should be warmed gently in a mixture of equal parts of glycerine 

 and potash solution, before being mounted in glycerine and 

 ammonia. 



When thus dealt with, favourable preparations allow the follow- 

 ing points to be demonstrated, both in the cortical and the central 

 tissue. 



{a) At the ends of the cells, i. c, at the point where two 

 adjacent cells are united, there is an annular thickening on the 

 internal wall not unlike a strongly developed ring of an annular 

 vessel. The material of which the ring is composed differs from 

 that of the cell walls in not dissolving or undergoing gelatinisation 

 under the influence of reagents. It seems to resist alike the 

 action of the strongest acids and the strongest alkalies, as well as 

 the disintegrating action of a solution of bleaching powder. 



{b) Within this ring the arrangements are not the same in all 

 cases, but for the most part they conform to one of four types. 



(i.) In the first type the ring surrounds a comparatively wide 

 and open pore, through which the protoplasm is continuous in a 

 single thread. This type is not very common, but isolated 

 instances are here and there to be met with. (PI. 255, Figs. 3 

 and 4). Grave doubts having been expressed respecting the exis- 

 tence in other plants of this type of continuity, special care has 

 been taken to prevent error on this point, which is admittedly of 

 great importance. The result is, that in the mind of the writer 

 there is perfect conviction that the description is in strict accord- 

 ance with the actual facts. In one extremely favourable pre- 

 paration, the thick ring is presented in section at both ends of a 

 cell, and the connecting cord of protoplasm is seen in situ, running 

 through the pores thus formed. This is shown in PI. 255, Fig. 4. 



(ii.) In the second type a delicate diaphragm stretches across 



