THE HIGHER CRYPTOGAMIA. 353 



bundles of the leaf and of the root separate at their edges, 

 and the intercellular cavities become filled with air. The 

 tissue which is filled with air soon dries up ; at last it 

 disappears altogether, and large air-cavities are formed ; — 

 four cylindrical cavities parallel to the axis are formed in 

 the leaf, and are divided into a series of compartments by 

 persistent cellular surfaces ; in the root one large air-cavity 

 is formed in front of, and near to the excentrical vas- 

 cular bundle. 



Whilst the base of the second leaf begins to form a 

 sheath round the terminal bud, the latter produces the 

 third leaf at a point opposite to the second, and above the 

 first (PL XLVII, fig. 3). At the same time the forma- 

 tion of the second root commences. It originates under 

 the second leaf, opposite to the first root, very near to the 

 first node, and is produced by the multiplication of a cell 

 adjoining the string of cells which goes to form the vascular 

 bundle. It is formed in precisely the same manner as the 

 first root, with which it makes an angle of about 30° open- 

 ing downwards. A plane passing through the longitudinal 

 axis of the first and second leaves and of the first root, 

 usually bisects the second root also ; small lateral deviations 

 are however not uncommon. The root in its longitudinal 

 development stretches the outermost cellular layer of the 

 rudimentary stem of the germ-plant to a considerable ex- 

 tent before it breaks through it (PI. XLVII, fig. 3). 



The rudiment of the third root, like that of the first and 

 second, only becomes visible when the third leaf has 

 already attained a certain degree of longitudinal develop- 

 ment. It is produced, like the second, by the multiplica- 

 tion of a cell adjacent to the lower end of the precursor of 

 the vascular bundle, and to the rudimentary ligneous body 

 of the germ-plant, and originates consequently on the left 

 hand, close above the place of origin of the first root. In 

 its development it turns itself at once somewhat side- 

 ways ; it makes its way through the cortical tissue of the 

 stem of the germ-plant in a direction which diverges about 

 30° laterally from that of the first root. 



The fourth and the following leaves, at least as far as the 



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