graduates into the common form in which the carpels are almost entirely
enveloped within the receptacle. In _C. moschata_ the ovarium (p. 50)
varies greatly in shape, being oval, nearly spherical, or cylindrical,
more or less swollen in the upper part, or constricted round the
middle, and either straight or curved. When the ovarium is short and
oval the interior structure does not differ from that of _C. maxima_
and _pepo_, but when it is elongated the carpels occupy only the
terminal and swollen portion. I may add that in one variety of the
cucumber (_Cucumis sativus_) the fruit regularly contains five carpels
instead of three.[754] I presume that it will not be disputed that we
here have instances of great variability in organs of the highest
physiological importance, and with most plants of the highest
classificatory importance.

Sageret[755] and Naudin found that the cucumber (_C. sativus_) could
not be crossed with any other species of the genus; therefore no doubt
it is specifically distinct from the melon. This will appear to most
persons a superfluous statement; yet we hear from Naudin[756] that
there is a race {360} of melons, in which the fruit is so like that of
the cucumber, "both externally and internally, that it is hardly
possible to distinguish the one from the other except by the leaves."
The varieties of the melon seem to be endless, for Naudin after six
years' study has not come to the end of them: he divides them into ten
sections, including numerous sub-varieties which all intercross with
perfect ease.[757] Of the forms considered by Naudin to be varieties,
botanists have made thirty distinct species! "and they had not the
slightest acquaintance with the multitude of new forms which have
appeared since their time." Nor is the creation of so many species at
all surprising when we consider how strictly their characters are
transmitted by seed, and how wonderfully they differ in appearance:
"Mira est quidem foliorum et habitus diversitas, sed multo magis
fructuum," says Naudin. The fruit is the valuable part, and this, in
accordance with the common rule, is the most modified part. Some melons
are only as large as small plums, others weigh as much as sixty-six
pounds. One variety has a scarlet fruit! Another is not more than an
inch in diameter, but sometimes more tha