, of Carpentras, on the
production of oak truffles in France. The acorns of evergreen and of
common oaks were sown about five yards apart. In the fourth year of
the plantation three truffles were found; at the date of the report
the trees were nine years old, and over a yard in height. Sows were
employed to search for the truffles. Although these plantations
consist both of the evergreen and common oak, truffles cannot be
gathered at the base of the latter species, it so happening that it
arrives later at a state of production. The common oak, however,
produces truffles like the evergreen oak, this report states, for a
great number of the natural truffle-grounds at Vaucluse are planted
with common oaks. It is remarked that the truffles produced from
these are larger but less regular than those of the evergreen oak,
which are smaller, but nearly always spherical. The truffles are
gathered at two periods of the year; in May only white truffles are to
be found, which never blacken and have no odour; they are dried and
sold for seasoning. The black truffles (_Tuber melanosporum_) commence
forming in June, enlarging towards the frosty season; then they become
hard, and acquire all their perfume. They are dug a month before and a
month after Christmas. It is also asserted that truffles are produced
about the vine, or at any rate that the association of the vine is
favourable to the production of truffles, because truffle-plots near
vines are very productive. The observation of this decided M. Rousseau
to plant a row of vines between the oaks. The result of this
experiment altogether does not appear to have been by any means
flattering, for at the end of eight years only little more than
fifteen pounds were obtained from a hectare of land, which, if valued
at 45 francs, would leave very little profit. M. Rousseau also called
attention to a meadow manured (_sic_) with parings of truffles, which
was said to have given prodigious results.

The cultivation of minute fungi for scientific purposes has been
incidentally alluded to and illustrated in foregoing chapters, and
consequently will not require such full and particular details
here. Somewhat intermediately, we might allude to the species of
_Sclerotium_, which are usually compact, externally blackish,
rounded or amorphous bodies, consisting of a cellular mass of the
nature of a concentrated mycelium. Placed in favourable conditions,
these forms of _Sclerotium_ will develop t