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A PECULIAR BULB OF ALLIUM SATIVUM LINN.
BY
P. M. Debbarman,
Royal Botanical Gardens, Calcutta.
In the course of a further search for teratological specimens, the writer has lately come across a peculiar bulb (figs. A-D) of Allium sativum L. It differs from a normal bulb (E) in having a small supernumerary bulb (Y) composed of a few bulblets, nicely fitted to the top of a large primary bulb (X) consisting of severel bulblets. On detaching some of the bulblets from the primary bulb (X) it was found that the bulblets of the supernumerary bulb (Y) were attached to the upper part of a curved prolongation (Sc) of a short discoid stem (St) hidden from view.
The question that naturally suggests itself here is — What has given rise to the supernumerary bulb (Y) ? At first sight one is apt to take it as an instance of ‘Displacement of bulbs’ (l) possibly due to luxuriant growth. But, considering the normal size and shape of the primary bulb (X) and of the bulblets composing it, and the absence of any bulblets on the intervening portion of the scape (Sc) between the bases of X and Y, it seems hardly probable that there could have been present any cause leading to overcrowding and ultimate displacement of the bulblets to the position occupied by Y.
It is, however, a well-known fact that, even in a normal inflorescence of Allium sativum the flowers are sometimes mostly supplanted (2) by bulbils (see fig. F). These bulbils are hardly distinguishable (3) from the ordinary bulblets composing a normal bulb. It seems quite probable that, being placed under some adverse circumstance {e.g. storage during the flowering season) the primary bulb (X) could not get sufficient nourishment to give rise to a normal-sized scape bearing a normal inflorescence. It stands to reason that under unfavourable circumstances a plant will naturally prefer to take recourse to the vegetative instead of the sexual mode of reproduction, there being no facility for the latter to come into play. It was probably in this way that the flowers on the abortive inflorescence (Y) were totally replaced by bulblets, which were quite well-suited for the former mode of reproduction. The zigzag shape of the scape (Sc) seems to lend support to this view.
