AN EXAMPLE OF LEAF‐ENATION IN ALLIUM URSINUM L

I N May, 1922 the late Mr Arthur Shrubbs, of the Cambridge Botany School Museum, found an interesting example of a leaf of Allium ursinum L., which had developed a second "lamina" on the lower surface. It was found growing on a boggy patch of ground near the Whittlesford Railway Station, about eight miles from Cambridge. Unfortunately, the specimen as brought into the laboratory was not complete, as the underground portion of it was left behind. In spite of a careful search by me in the same place a few days afterwards, the underground portion could not be discovered on account of the thick undergrowth, nor was any other similar specimen found. It was suggested to me that the vascular anatomy of the leaf might be interesting to work out, so I gladly undertook to do it. This paper embodies the result of the investigation. According to Mr Shrubbs's observation, the leaf while on the plant took up nearly an upright position, so that both its surfaces were turned more or less towards the light. "Petiole" and "lamina" were alike abnormal in structure. The "petiole," instead of being semicircular in section, as in normal examples of Allium ursinum, was flattened and appeared as if made up of two fused "petioles." In a transverse section at the base of the ai rial region it showed three prominent "ribs," one central and two marginal (Fig. 2). The central one continued into the "laminar" portion as the "midrib," and developed on the lower side the second blade. This lower blade was formed up to the very apex of the leaf, but was only half as broad as the upper one. The two marginal ones continued into the upper blade up to the very apex and formed two lateral prominent "ribs"