Mr. A. Henfrey on the Development of Vegetable Cells. 367 



One thing at least is certain, that the cytoblast has nothing to 

 do with the production of the permanent cell-wall, since it is al- 

 ways within the primordial utricle, either adhering to its walls or 

 at earlier periods suspended in the cavity by mucilaginous fila- 

 ments. 



In the course of my investigations to satisfy myself of the cor- 

 rectness of the view I had taken of the agency exercised by the 

 primordial utricle in cell- division, I have observed the process in 

 several plants, Cryptogamous and Phanerogamous. In no case 

 have I been able to trace the gradual progress of the formation 

 of septa so well as in Achimenes grandiflora. This plant pro- 

 duces a great number of axillary buds or bulbels, on the scales of 

 which are found many capitate hairs. I examined these hairs in 

 young buds of from about half a line to a line in length, possess- 

 ing at that period only six or seven scales. By dissection these 

 scales were isolated and brought under the microscope ; the hairs 

 which fringed the margin of the scales were thus presented free 

 throughout their whole length, and being very transparent af- 

 forded an admirable opportunity of examining the cells in their 

 different stages in a perfect and uninjured condition — an import- 

 ant point which cannot be secured in sections of growing tissues. 



In the earliest stage represented in the plate, the nuclei 

 were perfect and distinct one from another ; in the next, the 

 transverse lines indicate the commencement of the infolding of 

 the primordial utricle ; that the lines are not septa is seen by the 

 appearance of hairs which had been kept in spirit several days ; 

 in these, the primordial utricle, detached from the lateral walls, 

 is continuous throughout the whole length of the hair. 



Different stages of the infolding, that is, the progress of the fold 

 toward the centre, are shown by the constrictions exhibited by the 

 coloured mucilaginous cell-contents. In the specimen treated with 

 iodine, PI. VIII. fig. 8, the septa are incomplete in the upper part 

 of the hair, but the lowest septum is perfect, the primordial utricle 

 with the cell-contents having become retracted from it. In this 

 septum, the two new layers may be traced from the lateral walls, 

 intimately united toward the centre so as to appear like one layer. 

 This example also shows that the layers forming the septum are 

 continuous with a new layer deposited over the inside of the 

 lateral wall. Mohl states that each layer of new matter grows 

 from the circumference to the centre, and that the septum is not 

 produced by a succession of layers each projecting a little beyond 

 that preceding it. This point I have not yet been able to deter- 

 mine for myself. In the perfect cell, the primordial utricle with 

 the nucleus undergoes dissolution. 



These views, which I have adopted of the nature of the process 



