DEVELOPMENT OF ALLIUM URSINUM. 93 



transverse section (Fig. 4, e) as a curved fissure whose convex side 

 is directed forwards. At the bottom of this cavity a little bud 

 (Fig. 3, g) is found. The form of the bulb is derived from this 

 sheath, since that of the first leaf, in consequence of its membra- 

 naceous substance, adds little to the thickness. 



After flowering the leaves quickly fade ; the first leaf by autumn 

 is completely gone, so as to leave not even a vestige of the sheath. 

 Such is the case also with the peduncle. The second leaf perishes 

 only as far as the commencement of the sheath, leaving there a 

 roundish scar. The sheath itself remains fresh and fleshy. In 

 autumn the vegetation of this bulb awakes, which had been dor- 

 mant through the summer ; it sends out from its base through the 

 fleshy sheath filiform roots, one of which frequently ascends through 

 its bore, and makes its way through the aperture above. The 

 before-mentioned bud begins to elongate, and in November has 

 frequently reached half the height of the sheath. Its outer part 

 is a membranaceous sheath whose aperture is at the apex. It 

 alternates with the sheath which incloses it. After its removal 

 either a second similar sheath appears, or, what is more frequent, a 

 still tender leaf, the closed sheath of which is very evident. The 

 margins of its lamina are rolled inwards, and the medial nerve is 

 very strong and broad on its upper surface ; near it on either side 

 the involute margin. On the under side, on the contrary, the nerve 

 does not project. The leaves of Alstrcemeria Pelegrina and other 

 species of the genus, in which the under side is smooth and the 

 upper marked with many raised nerves alternately higher and 

 lower, exhibit the same phases. The proper under surface becomes 

 the upper surface by means of the twisting of the lamina. From 

 the sheath of this first leaf the very short flower-stem projects : 

 it bears at its apex two bracts, of which, the outer alternates with 

 the first leaf, the inner stands opposite to it. Both at a later period 

 become connate and form the involucre. In the axil of the first 

 a second but smaller leaf is found, which is turned with its back 

 towards the stem. 



In spring, when the sheath, which is two to three inches long, and 

 the two leaves (the second of which expands somewhat later than the 

 first) and the flower-stem spring forth, in which the leaves undergo 

 the above-mentioned bending and twisting, the fleshy sheath 

 which remained from the second leaf of the foregoing year is 

 gradually absorbed, so that nothing remains except the bundles, of 

 vessels by which they were threaded ; hence arise the bristles 

 which were mentioned above. The sheath also which origiuallv 



