378 ON THE CONSTITUTION AND FUNCTIONS OF BULBS. 
tubercle—that is, the germ of the offset, or new bulb, intended to be 
developed in the next growth. There are also various marks scattered 
all over the bulb, without regular order, and of different sizes, formed 
of very fine coats, and containing small germs, which are developed 
according to the quantity of nourishment received by the parent bulb, 
and which sometimes may, perhaps, become abortive, when the parent 
bulb is too small to afford them support. 
“ The bulb, if cut open in this dormant state, only presents a homo¬ 
geneous milk-white mass, the organisation of which is invisible. When 
it begins to vegetate it sends out circumferential fibrous roots, and 
developes one or more germs, which increase into one or more little 
bundles, each formed of a sheath, enclosing leaves, and the largest con¬ 
taining also the flower. These little bundles have a slight expansion 
at the base, which, being cut through lengthwise, discover a smaller 
bulb surrounded by coats, the outer of which proceed from the sheaths 
above mentioned, and the inner ones from the bases of the leaves, 
and both, combined, forming a small solid substance.” 
This small solid substance ultimately becomes the new bulb to 
flower in the following year. Dr. T. has traced the whole process of 
the change presented by the old bulb while it is nourishing its leaves, 
flower, &c., and at last feeding off its successor, while the parent itself 
dwindles away to a small mass of dead fibres. 
In the case of real bulbs, as the tulip, for instance, we find it, before 
expansion, to consist of what is called the radical plate, on which are 
seated a congeries of thick fleshy scales, involving each other, and 
embracing the embryo flower and leaves in the centre. When this 
latter portion is developed in the summer, a successor rises from the 
radical plate close beside it, to take the place of the first, which totally 
disappears at the end of the flowering season; thus showing that all 
the succession-bulbs originate in the radical plate. 
Considering, then, what Dr. T. has shown relative to the structure 
of the crocus tuber, it is evident that, in the first stage of its develop¬ 
ment, it acts like a radical plate, but with this difference, that, whereas 
the crocus tuber wastes entirely away, the plate of the tulip is perma¬ 
nent, suffering no diminution, except the bottom slough, which is dis¬ 
charged along with the fibres which served to draw nourishment during 
the growth. 
Dr.T. observes that the tubers of the Gladiolus communis are renewed 
much in the same way as those of the crocus. The Colchicum autum- 
nale also differs but little from the crocus, only that, instead of the new 
bulb being produced on the crown of the old one, it is produced at the 
side, and, “ having a free base, they immediately, without passing through 
