Development, and Structure of the Vegetable Cell. 27 



subsequently a green hue, a new reside in the mean time being 

 developed in the centre of the cell. 



Kiitzing's hypothesis receives support from, and was probably 

 based upon those varieties in development in which the chloro- 

 phyll-bands are in close apposition and not very obhque in di- 

 rection, as seen in figs. 69 and 70, representing the Spirogyra 

 orthospira, Nageli (?) {S. majusculn, KUtzing?). In these ex- 

 amples the recognition of the limits of the several bands, and 

 of the untenability of this view; is difficult, but it may l)e 

 attained by the observation of the further development. 



On cutting through a joint-cell, as shown in tig«. 70 aud 72, 

 and observing the contents as soon as possible after the water 

 first begins to act tr i, we see, according to the phase of 



development of the ^ 1, the extrusioti from the interior of 



a number of larger or smaller hyaline cells ; the chlorophyll- 

 bands usually break up into several elongated or spherical cells, 

 which swell up more or leas rapidly, display one or several very 

 thick-walled starch-vesicles imbedded in the green mucoid con- 

 tents, and, on fully emerging from the joint-cell into the 

 water, suffer collapse. On the contrary, the mucoid mass 

 which inve«»- *^'' ^^y^>\\t•„. o^.\\n resists the solvent action of the 

 water. 



Some of \i\< are usually very much larger 



than the rest, t x'ing, as a rule, present in each 



joint-cell, one or two lying on either side of the cell-nucleus. 

 Betwixt these, surrounding the cell-nucleus, are placed the 

 smaller and similar cells. These structures are, in rarer in- 

 stances, found at the ends of the cells near the septum (fig. 72). 



In those species in which the nuclear cell multiplies simul- 

 taneously with the formation of new Joint-cells, as in Sp ir ofy m 

 nitida, S. orthospira, Sec, only one of these non-nuclear endo- 

 genous cells is enlarged on either side of the cell-nucleus ; 

 whilst in those other species, where the nucleus is little deve- 

 loped, two such endogenous cells are mostly to be seen on either 

 side of it. 



In fig. 72, one of these large colourless cells has been de- 

 stroyed in making the section through the uppermost joint-ceil 

 in the vicinity of the septum ; but the second has been consider- 

 ably extended, and the smaller hyaline cells, which originally 

 occupied the centre of the joint-cell, have been displaced 

 by it. 



The water also acts similarly, although more gradually, upon 

 the cell next to that which has been cut through, no doubt by 

 penetrating through the exposed septum (figs. 71 and 72). In 

 the corresponding cell (Hg. 72) one of the two large colourless 

 cells has protruded itself at each side of the joint near the sep- 



