[1]
[Footnote 1: Reader in Botany. VI. The Relative Positions of Leaves and
Rootlets.]
5. _Comparison of a Carrot, an Onion, and a Potato_.--It is a good
exercise for a class to take a potato, an onion, and a carrot or radish to
compare, writing out the result of their observations.
The carrot is a fleshy root, as we have already seen. The onion consists
of the fleshy bases of last year's leaves, sheathed by the dried remains
of the leaves of former years, from which all nourishment has been drawn.
The parallel veining of the leaves is distinctly marked. The stem is a
plate at the base, to which these fleshy scales are attached. In the
centre, or in the axils of the scales, the newly-forming bulbs can be
seen, in onions that are sprouting. If possible, compare other bulbs, as
those of Tulip, Hyacinth, or Snowdrop, and the bulb of a Crocus, in which
the fleshy part consists of the thickened base of the stem, and the leaves
are merely dry scales. This is called a _corm_.
The potato is a thickened stem. It shows itself to be a stem, because it
bears organs. The leaves are reduced to little scales (eyelids), in the
axils of which come the buds (eyes). The following delightful experiment
has been recommended to me.
In a growing potato plant, direct upwards one of the low shoots and
surround it with a little cylinder of stiff carpet paper, stuffed with
sphagnum and loam. Cut away the other tuber-disposed shoots as they
appear.
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