Development t and Structure of the Vegetable Cell. 29 



the cell, where the primary cell-membrane is still adherent to the 

 secondary. 



If a vigorously growing Spiroffi/ra, after the first operation of 

 the diosmotic fluid has effected the complete separation of the 

 secondary cells from the nieinbraue of the primary, be laid in 

 pure water, the secondary cells, with their contained tissue of 

 cells, appear to regain their former position. 



If the diosmotic fluid be allowed to effect a complete contrac- 

 tion of the secondary cells, and the surrounding liquid be then 

 rapidly replaced by pure water, the secondary cells do not again 

 expand (either from the entire exosmosis of their contents or 

 from the rupture of their walls), but the non-nuclear daughter 

 cells (vesicles) then break through the membrane of the second- 

 ary cell and progressively expand, the larger of them usually 

 again entirely occupying the cavity of the mother cell, and 

 proceed to form a septum at the middle by the juxtaposition of 

 their walls. 



In this case the same phenomena occur as mechanical effects 

 which have been observed as the normal process of growth in 

 the continuously developing daughter cells of (Edoffmhtm, If 

 the experiment be made with Sjnrogyrtt in a state «f TegetatiYe 

 repose, in which the endogenous cells are less developed and do 

 not entirely fill the mother cell, then, during the exosmotic con- 

 traction of the secondary cell, its membrane is torn completely 

 across in the middle of the two enclosed daughter cells, together 

 with the portion of the chlorophyll-sac which is here situated. 



Under such circumstances, moreover, the daughter cells, after 

 the addition of the water, protrude from the spiral sac and those 

 portions of the envelope of the mother cell that covered them, 

 and proceed to expand in the manner described, constituting 

 that condition which has hitherto been erroneously supposed to 

 originate from fission of the secondary mother cells (figs. 78 & 

 79, from S. quinina). 



These different diosmotic reactions exhibited by the several 

 nested cells within a joiut-cell are probablv dependent on the 

 different nature of their membranes, as indicated by their dif- 

 ferent degrees of thickness and firmness, and probably also on 

 the varying quantity of their component elements, which are 

 cognizable by no chemical distinctions. 



Both the primary and secondary cells of a joint-cell, and also 

 the non-nuclear transparent daughter cells, contain a material 

 which is coloured blue like starch by an aqueous solution of iodine, 

 after maeeration not only with dilute solution of sulphuric acid 

 or chloride of zinc, but also with a neutral solution of chloride 

 of calcium. In this state it is commonly more or less slightly 

 turbid, like finely divided starch. The contents of the primary 



