42 M. L. Garreau on the Functions of 



ranee of a portion of tlic labours which had been devoted to it ; 

 and it was in the course of my investigation of the nucleus and 

 the intracellular canals that I was led to the discovery of this 

 lamina of the cell in all growing as well as in mature cells 

 when these latter are not too largely coated by encrusting 

 deposits. 



This lining-membrane of the cell, being immediately in con- 

 tact with the external wall, cannot be distinguished whilst pre- 

 serving its normal relations, and requires the action of reagents 

 to display it. The solution of iodine in iodide of potassium 

 colours it more or less deeply yellow, as it does the nucleus and 

 its processes. In the same manner it is coloured red by the 

 acid nitrate of mercury, and is contracted by the action of acids 

 and of alcohol, indicating in these reactions its similarity in che- 

 mical composition to the nucleus and the canals diverging from 

 it. When it has been detached from the external lamina of the 

 cell by means of alcohol, it presents itself under the form of a 

 delicate flexuose sac, of extreme tenuity, and without appreciable 

 structure. However, the same appearances are not met with 

 when the examination is conducted without recourse to reagents, 

 as it may be in the cells of the transparent hairs oi Lamium, where 

 the lining-membrane undergoes spontaneous detachment at 

 some points of its periphery, if the hairs are allowed to wither a 

 little. In cells so treated, the relations of this inner membrane 

 being only slightly modified, and its vitality not being destroyed, 

 it becomes a more easy task to prosecute its study, and the ob- 

 server may very soon and easily convince himself that it is hol- 

 lowed out by minute canals permeating its substance, the most 

 capacious of which outspread themselves upon its internal aspect, 

 whilst the most slender constitute a close network of anasto- 

 mosing tubercles within its thickness. Nevertheless it is not 

 necessary, in the case of the cells of the plant mentioned, to wait 

 for the partial detachment of this lamina ; for the observer, when 

 apprised of the existence of this structure, may satisfy himself 

 of its characters whilst the membrane still retains its normal 

 position. 



When the primordial membrane is partially detached from 

 the cell-wall, a very careful examination of the little spaces left 

 between it and the external wall, where the separation is least 

 wide, will reveal the presence of certain very slender filaments 

 implanted in this outer wall ; and upon slightly removing this 

 same wall a little out of the focus of the instrument, these fila- 

 ments may be perceived to form salient lines more illuminated 

 than the rest of the cell-wall — a phenomenon which could not 

 present itself if these filaments were situated in the detached 

 portion of the primordial membrane itself. If I am not in error 



