534 On the Nature and Causes of the Decay in Potatoes. 
and seeing them in apparentl y good condition, he told his gardener 
to send him a dish. It is related that the gardener plucked the 
green apples, which were sent to Sir Walter's table, who, finding 
them very disagreeable, was convinced some weeds liad been sent 
instead of the fine American fruit, so he directed his gardener to 
weed them out of the garden. Whilst doing so the tubers were 
observed hy Sir Walter, who immediately recognised them and 
directed their future cultivation. Still they got slowly on. Nor 
could they have been extensively used long after this, for Girard 
in his 'Herbal' describes the potato as " a plant from America 
winch is an excellent thing for making sweet sauces, and also to be 
eaten with sops and wines. " 
In 1684 the plant was pretty extensively cultivated in Lanca- 
shire, but it was not till 1728 that the first field-crop was culti- 
vated in Scotland, and it was not extensively grown in that country 
till 1732. In Scotland the potato met with virulent hostility by 
the religious zealots of that time, who argued that it was a sinful 
plant because it was nowhere mentioned in the Bible. Since 
these periods it is needless to describe to you how rapidly the 
culture of the potato has spread in this country, or how essential 
it now is to a large portion of its population. 
The potato-plant, or, as it is called by botanists, the Solamim 
tuberosum, belongs to that order of plants of which you may take 
deadly nightshade as an example. The potato itself is vulgarly 
supposed to be the root of the plant, and fifteen or twenty years 
since even botanists themselves seemed inclined to consider it as a 
root. If a seed of the potato is planted, it puts forth roots like 
any other seed, but these roots never enlarge into a tuber. The 
tuberous enlargement called the potato is in fact part of the 
underground stem of the plant, which enlarges into this form by 
the increase of the cellular tissue. The potato, hke all other 
plants, is made up of three parts — the cellular tissue, the vascular 
tissue, and a kind of cuticle or skin. Now the enlargement of 
the underground stem is effected by the great growth of the cel- 
lular tissue, while the skin is capable of extension to a certain 
extent so as to admit of the enlargement.* The vascular tissue 
(vide Fig. II.) does not however increase except in the vascular 
bundles becoming longer and extending themselves throughout 
the cellular part ; that is, they do not increase in their number. 
The cellular tissue is that to which we have to devote more 
special attention as far as regards the direct subject of the lectures. 
A number of cells of very various shapes are thrown irregularly 
and apparently indiscriminately the one upon the other ; they are 
* A very elaborate memoir on this subject, by Turpin, will be found in 
the nineteenth voUime of the " Menioires du Museum, ' page i. 
