LIFE OF THE PLANT-CELL 



123 





109 



64. The cells of the root sheath contain only air, and probably 

 serve for the condensation of the aqueous vapour, and the con- 

 veying of it to the parenchyma of the root. 



Here we have again an unsolved mystery of which I can give no other 

 explanation, although the consideration of the conditions under which 

 these roots occur in plants, growing for the most part without earth in 

 an atmosphere saturated with moisture, may throw some light upon the 

 subject. I do not allow much importance to the supposed great hy- 

 groscopicity of the spiral fibres, which is always put prominently forward 

 by Meyen ; but attribute more to the extreme porosity of this layer, which 

 probably acts in the same way as freshly burned charcoal. 



los Perpendicular section through the epidermis (e?) of the leaf of Fiats Carica, by 

 which two hairs (a and &), with dilated basal portion, are laid open. In the figure, the 

 point of b is left. Both hairs are filled towards the upper part by gradual deposits, 

 and these concretions (c) hang down into the basal dilatation of the hair-cell. In the 

 hair marked b, this concretion consists of three united portions. 



!09 Section perpendicular to the surface of the leaf of Humulus Lupulus, through 

 the epidermis (b), and some of the subjacent parenchymatous cells, a, An epidermis- 

 coll dilated inwardly into a vesicle, analogous to the hairs of Ficus. The narrower 

 extremity is filled up, and from this part depends by a sort of peduncle a concre- 

 tionary mass into the dilated portion of the cclL 



