Structure and Division of the Vegetable Cell. 211 



growth of the septum on the chlorophyll bands. These, 

 along with the protoplasm, bend inwards for a certain 

 length, their continuity not being at all interfered with, 

 so that, on focussing down, one can catch a clear image 

 of the outer edge of the septum, and also many of 

 the chlorophyll bands, but one or more are indistinct as 

 they approach the septum, and further focussing must be 

 resorted to ere their complete course is traced (Plate X. 

 fig. 12). About the time that the septum has grown in 

 to meet the cell-plate they are severed in a very inexpli- 

 cable way, the severed edges giving the impression that 

 they are neatly cut or gnawed through, not at right angles 

 to the bands, but obliquely, though quite in a line with the 

 advancing septum. These cut ends must continue to grow, 

 since, later on, instead of their being opposite each other, 

 one may be considerably prolonged round the interior of 

 the cell. 



The nuclear barrel, as far as we have yet considered it, 

 may be said to have passed through the 'waxing phase, but 

 henceforth it gradually diminishes in width, and may 

 appropriately be described as assuming tlie ivaning phase. 

 We for the time left studying the septum, after watch- 

 ing it till it had grow^n in to meet the edge of the cell- 

 plate all round. As growth in width proceeds, it passes 

 into the clear band between the granules of the cell- 

 plate, and these, as I suppose, taking on the function of 

 the protoplasmic granules, advance centripetally with the 

 growing edge of the septum, causing thereby a waning of 

 the barrel. The first part of this condition of things is 

 brought out in Plate X. fig. 116, copied from a most beauti- 

 ful isolated nucleus in one of Mr Jackson's slides. Here 

 we see the part o^the septum, formed by infolding of the 

 peripheral protoplasm, protruding on each side, as viewed 

 optically, or projected flat, though it is in reality a circular 

 projecting rim. From its being projected flat, it is of 

 course impossible to bring out — what is easily accomplished 

 by gradual focussing down — the appearance of a centripetal 

 development of it. In Plate X. figs. 13 and 14, this is 

 partially successful, as by compression the cells are pressed 

 slightly to one side. Waning of the nuclear barrel and 

 deepening of the septum continue till the two daughter 



