lated.[509] In these seeds
the outer coating becomes very thick and fleshy, and is traversed by
spiral vessels.

It is obvious that very important results in a practical point of view
may be and have been arrived at by cultivators availing themselves of
this tendency of plants to increase in dimensions under certain
circumstances. It is needless to do more than refer to the many fruits,
vegetables, and cereals, which have thus become enlarged and improved by
careful selection and rearing.

=Alterations of consistence= often accompany changes in size. The change
may be one whereby the tissues become unusually hardened, by the
excessive formation of secondary woody deposits, or softer and more
succulent than ordinary, from the formation of an inordinate amount of
loose cellular tissue. Generally speaking, the appearances presented in
such cases are not sufficiently striking to demand notice other than as
regards their size. One illustration, however, may be cited from its
singularity. This was the case of a dahlia, in which the centre of the
flower was occupied by a projecting knob as large as a walnut, brown in
colour, and very hard in texture. This knob was nothing but the enlarged
and indurated extremity of the common receptacle, destitute of the
scales and florets which usually spring from it. No insect-puncture
could be detected, and no other reason for this peculiarity could be
ascertained.

FOOTNOTES:

[488] On the subject of knaurs, the reader is referred to Trecul, 'Ann.
Sc. Nat.,' 3 ser., vol. xx, p. 65; Lindley, 'Theory of Horticulture;'
Rev. M. J. Berkeley, 'Gardeners' Chronicle,' 1855, p. 756.

[489] Jaeger, 'Flora.' 1860. p. 49, tab. i.

[490] 'Revue Horticole,' 1868, p. 110, figs. 12, 13.

[491] The reader may also refer for further information on the subject
of malformed pears to Irmisch. 'Flora,' 1858, p. 38, tab. i; Lindley,
'Theory of Horticulture'; Caspary, 'Bull. Soc. Bot. France,' vol. vi,
1859 (Rev. Bibl.), p. 235; Duhamel, 'Phys. Arbr.,' liv. iii, cap. 3. p.
393, fig. 308; Bonnet, 'Recherch. Us. feuilles,' tab. xxvi, fig. 2;
Moquin-Tandon, 'El. Ter. Veg.,' p. 384, &c. Some of the cases recorded
are, however, instances of true prolification.

[492] 'Revue Horticole' 1868, p. 310.

[493] The interest of this accident is great, as showing how an
habitually superior ovary may become inferior--a change so rare in its
occurrence that its existence has been denied, and thus forming a marked
co