278 STIPULES LIGULA. [BOOK i. 



several incomplete envelopes (leaves). On removing these 

 the nucleus of the axis appears as a naked tumour, having, at 

 a certain period, a furrow situated nearer its periphery than 

 its centre ; behind this furrow a convex excentricity is after- 

 wards formed. This convex part gradually rises, so that its 

 highest point passes beyond the summit of the axis, is con- 

 tinued obliquely on each side on the periphery of the axis, 

 and at last closes on the point opposite it : in this state it 

 forms a rim clasping the axis, and continuous with the 

 original excentricity, which now forms a boss distant from 

 the axis, which it goes beyond. A little later the whole 

 of this organ is distinctly furrowed, which is owing to the 

 cells being disposed in lines. The annular rim then elon- 

 gates and forms a sheath, and, at the same time, the 

 boss is developed into a foliaceous envelope covering the 

 axis or the less advanced leaves that are immediately 

 continuous with the sheath. The edges of this envelope 

 never grow together; but when they are grown so large 

 as to touch one another, one grows beneath the other, 

 so that the completely formed leaf is rolled spirally over 

 the parts beneath. In this stage of the growth, the petiole 

 exists only as an undefined mass, and the ligula is not 

 perceptible. 



In some Grasses thac I have examined (as Barley and 

 Wheat), the formation of the leaves is the same as that just 

 described. The leaf grows in the form of a tumour, extends 

 itself over the periphery of the nucleus of the axis, eventually 

 surrounding it by its base, which becomes a sheath while the 

 upper part rises obliquely on the axis. Whilst the blade of 

 the leaf is still applied above to the top of the axis, a slight 

 rim is formed on its inner surface, immediately above the top 

 of the axis ; the base of this rim occupies at least two-thirds 

 of the breadth of the blade of the leaf. On isolating the blade, 

 the rim appears as a projecting line in which series of cells 

 can be distinguished; it is this rim that becomes the ligula. 



My researches on this subject are too limited to enable me 

 to decide whether the formation of the ligula is absolutely 

 identical with that of stipules in Dicotyledons. 



The conclusions to which my observations have led me, 



