506 MR. J. G. BAKER ON THE 
distinct. Of these 700 it is only six that grow potatoes at all, 
and the remainder all maintain their hold in the world as most 
plants do, by means of their flowers, fruits, and seeds. I do not 
think that the Chilian S. etuberosum and Mexican S. suaveolens 
are more than mere forms of S. tuberosum, and they are said to 
be quite destitute of tubers; and there is the fact noted by Sir 
J. D. Hooker, that when S. Maglia was first grown at Kew, for 
two years it did not yield any tubers. A great many of the culti- 
vated varieties rarely produce flower and fruit. Any plant brought 
to the tuber-bearing state is in a disorganized unhealthy condi- 
tion, a fitting subject for the attacks of fungi and aphides. The 
great difficulty with which we have to contend in fighting disease 
is that in the potato, as in other cultivated species, we grow 
in great masses plants which in a state of nature are scat- 
tered amongst others. The relationship of tuber to fruit 1s 
so clearly shown by one of the experiments of Mr. T. A. Knight 
that I will cite it in this connection. * Every gardener knows i: 
(he writes in * Philosophical Transactions,’ 1806, p. 297) “ that 
early varieties of the potato never afford either blossoms or 
seeds ; and I attributed this peculiarity to privation of nutriment, 
owing to the tubers being formed preternaturally early, and 
thence drawing off that portion of the true sap which, in the 
ordinary course of nature, is employed in the formation and 
nutrition of blossoms and seeds. I therefore in the last spring 
planted some cuttings of a very early variety of the potato, 
which had never been known to bloom in garden-pots, having 
heaped the mould as high as I could above the level of the pot, 
and planted the portion of the root nearly at the top of it. 
When the plants had grown a few inches high, they were secured 
to strong sticks, which had been fixed erect in the pot for that 
purpose, and the mould was then washed away from their stems 
by a strong current of water. Each plant was now suspended in 
air, and had no communication with the soil in the pots, except 
by its fibrous roots; and as these are perfectly distinct organs 
from the runners that generate and feed the tubers, I could 
readily prevent the formation of them. Efforts were soon made 
by every plant to generate runners and tubers, but these were 
destroyed as soon as they became perceptible. An increased 
luxuriance of growth now became visible in every plant, numerous 
blossoms were emitted, and every blossom afforded fruit." 
