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THE STRUCTURE OF A GARLIC BULB. 



E. G. HIGHFIELD, B.Sc. 



The wild garlic or Ramsons ( Allium ursinum) may, with 

 advantage, be chosen by students of botany as a suitable 

 plant in which to study the origin and structure of a bulb. 

 It is very plentiful, and bulbs in all stages of development from 

 germinating seeds upwards can easily be obtained in a wild 

 state. 



As compared with other bulbous plants, the garlic presents 

 several distinctive characteristics, particularly in the ■simplicity 

 of its parts, and the rapidity with which the bulb passes through 

 the stages of disintegration and reconstruction. Although 

 perennial, yet no part of the bulb is of more than one year's 

 duration. Vegetative reproduction is also very rapid, a new 

 bulb is separated from the parent stock in one season, and 

 may attain full maturity. Bulbs formed from seed, however, 

 require several years before they reach a flowering stage. 



Wherever a garlic bed is situated germinating seeds may 

 be found abundantly on the surface of the soil during February 

 and March. The seedling at once assumes the bulbous struc- 

 ture of the mature plant. The tubular base of the cotyledon 

 is the first part to emerge from the seed coat, it bends down- 

 wards, and produces at its base two or more strong contractile 

 roots which tend to pull the plant below the surface. 



Judging from the structure of a mature leaf, the cotyledon 

 may be supposed to consist of a lamina, a solid petiole and a 

 tubular base. The lamina remains within the seed coat, and 

 serves to digest the food storage from the endosperm, and to pass 

 it through the petiole to the tubular base, which swells and 

 thus forms the first stage of the bulb. The shoot arises within 

 the tubular base of the cotyledon, and passes out at the point 

 where the tube merges into the solid petiole. Eventually, 

 when the food supply of the endosperm is exhausted, the petiole 

 of the cotyledon withers and falls off, leaving a scar on one side 

 of the small bulb. 



The shoot consists of a sheath or tubular leaf base, sur- 

 rounding one perfect leaf. Only one leaf is produced during 

 the first year ; as this develops, the food is withdrawn from 

 the cotyledon ring, which begins to disintegrate, and soon 

 disappears entirely. When the leaf is expanded above ground 

 the food manufactured by the lamina is stored in the tubular 

 base of this leaf, and at the end of the season the lamina and 

 petiole wither and become detached from the leaf base, leaving 

 a scar at one side. The new shoot arises at the base of the 

 tube as before, and emerges at the point where the tube passes 

 into the petiole, thus producing on a larger scale a precisely 



1912 Nov. I. 



