grew darker and of a more ruddy yellow, and at the end of a
fortnight or three weeks the size of the abortive fruit rather exceeded
that of a ripe walnut. In fact, an observer might imagine himself to be
walking amongst trees laden with ripe apricots, but, like the fabled
fruit on the banks of the Dead Sea, these plums, though tempting to the
eye, when examined, were found to be hollow, containing air, and
consisting only of a distended skin, insipid, and tasteless. By-and-bye
a greenish mould is developed on the surface of the blighted fruit; then
the surface becomes black and shrivelled, and at the expiration of a
month from the time of flowering the whole are rotten and decomposed.
The flower appears about the beginning of June, and before August there
is hardly a plum to be seen. It is curious that where two flower-stalks
arise from one point of the branch, one will often go on to ripen in the
normal way, while the other will become abortive, as above described."

In a specimen described by Mr. Berkeley there were two distinct ovules
of equal size close to the apex of the fruit, connected with the base by
vessels running down the walls. It should be observed that there is a
worthless variety of plum, Kirke's stoneless, or Sans Noyau, in which
the kernel is not surrounded by any bony deposit.

[538] 'Bull. Soc. Bot. Fr.,' 1862, vol. ix, pp. 37 et 291.

[539] Carl Schimp, 'Fl. Friburg,' vii, p. 745; Hook, fil., 'Journ. Linn.
Soc.,' vi, p. 9.

[540] 'Linnaea,' vol. v, 1830, p. 493.

[541] Moquin-Tandon, 'El. Ter. Veg.,' p. 325.

[542] Alph. De Candolle states that the position of the abortive ovules
affords a good character for discriminating between certain species of
_Quercus_, 'Bibl. Univ. Genev.,' 1862, t. xv, p. 929.

[543] See Moore, 'Nature-Printed Ferns,' 8vo, for numerous illustrations
both of depauperate and exindusiate ferns. _Scolopendrium vulgare_ seems
to be one of the ferns most commonly affected in this way. Moore, loc.
cit., vol. ii, pp. 135, 147, 159, 165, &c.

[544] 'Bull. Acad. Belg.,' t. xvii, p. 38, t. 1; Lobelia, p. 85.

[545] Cited in 'Henfrey's Botanical Gazette,' i, p. 179.

[546] 'Origin of Species,' p. 450.

CHAPTER II.

DEGENERATION.

While the terms atrophy and abortion apply in the main to a mere
diminution of size, as contrasted with the ordinary standard,
degeneration may be understood to apply to those cases in which not only
is the absolute bulk diminished, but