l68 BOTANICAL MICROTECHNIQUE. 



296. Mangin (VI) obtained a deep staining of the middle 

 lamella on placing thin sections of adult plant-organs in 

 phenosafranin or methylene blue after treatment with the 

 above mentioned acid-alcohol mixture. The middle lamella 

 of pectic acid stains much more deeply than the pectic com- 

 pounds mixed with cellulose of the thickenings of the cell- 

 wall. 



9. Ash- and Silica-skeletons of the Cell-wall. 



297. The inorganic salts which incrust all vegetable cell- 

 walls are in many cases present in such quantity that, after 

 the destruction of all organic substances by burning, they 

 still preserve the form of the original membranes. 



Such ash-skeletons may easily be obtained by burning 

 cross-sections of the stem of Cucurbita Pepo on the cover- 

 _glass. But they must be examined in the air, as they are at 

 least partly soluble in water. These ash-skeletons consist 

 chiefly of potassium and calcium salts. In other cases silicic 

 -acid also occurs deposited in great quantity in the mem- 

 branes. For methods of recognizing this, see 78-81. 



10. On the Developmental History of the Cell-wall. 



297a. In the study of the growth of cell-walls it is often 

 important to stain the membranes without affecting the 

 vitality of the cells. If the objects thus treated are then 

 -allowed to develop further in pure' water, it would seem pos- 

 sible to distinguish the newly formed membranes or parts 

 of membranes from those previously formed, with certainty. 



Noll (I) proceeded, with this object, with Caulerpa and 

 some other marine algae by producing a precipitate of Ber- 

 lin blue or Turnbull's blue in the membranes of the plants 

 under investigation without injuring their vitality, and then 

 allowing them to grow more, under favorable conditions. 

 The newly-formed membranes must then, plainly, be color- 

 less ; and those which have grown, perhaps by intussuscep- 

 tion, must show a lighter color. 



297b. To produce a precipitate of Berlin blue in the 

 membranes, Noll (I, ill) placed the algae first, for one or a 



