I 



the Nitrogenous Matter of Plants. 41 



of the surrounding fluid. Alcohol of 86°, by acting upon them, 

 slightly diminishes their transparency, and at the same time 

 contracts them as it does also animal matter. If its application 

 be continued, it is no unusual occurrence to see some of them, 

 that are greatly distended, rupture and collapse, and retreat 

 thereupon towards the nucleus, or, if the rupture takes place 

 near the nucleus itself (which is a rare occurrence), towards the 

 cell- wall. 



Hydrochloric acid causes an equal contraction of them, and 

 at the same time diminishes their limpidity. The nitrate of the 

 binoxide of mercury contracts them in the same way, and imparts 

 to them the same rosy hue that it produces with all other albu- 

 minoid matters. Liquid ammonia and the other soluble bases, 

 when diluted, produce a contrary effect, causing them to swell 

 up, and tending to dissolve them. From these characters it is 

 evident that in chemical composition these canals resemble albu- 

 men, as well as the nucleus itself; indeed, it would be difficult to 

 conceive it to be otherwise, even were no reagents employed. 



This might be deemed the proper place to consider the inter- 

 nal causes which incessantly modify the appearance and relations 

 of these canals ; however, to avoid repetition, it seems preferable 

 to defer these matters to the second part of this paper. 



Hitherto only that portion of the nuclear apparatus which lies 

 freely in the cell -cavity has received attention in the foregoing 

 remarks ; we will now proceed to follow its connexion with the 

 cell-walls ; and in order more correctly to delineate these rela- 

 tions, it is important to recall some facts concerning the cell- wall 

 itself. As early as the year 1836, M. Girou de Buzareingues had 

 regarded the cell-wall, apart from the thickenings of its external 

 membrane, as composed of two distinct tunics, one within the 

 other. Subsequently Harting investigated this subject, and 

 especially studied the action of some chemical agents on the 

 membrane which circumscribes the cell-cavity, as well as on the 

 other two laminae which, according to that observer, are de- 

 posited on its external surface. From these experiments he 

 satisfied himself, as we moreover had done by our own researches, 

 that the internal membrane, which he named the ptychode, 

 behaves with iodine, alcohol, and acids precisely in the same 

 manner as the nucleus. Hugo Mohl also entered on this same 

 inquiry with his customary skill ; and his researches went to 

 prove that this internal membrane, which he called ^^ primordial, '' 

 is to be met with in all cells that are not too old or thickened by 

 deposits of encrusting matters. Lastly, Harting, in 1846, 

 showed that the internal membrane adheres only feebly to the 

 external wall of the cell. At the period (1845) when I directed 

 my attention to this internal membranous layer, I was in igno- 



