Seven cabbage seeds of the previous year were placed on the same number
of leaves. Some of these leaves were moderately, but the greater number
only slightly inflected, and most of them re-expanded on the third day.
One, however, remained clasped till the fourth, and another till the
fifth day. These leaves therefore were excited somewhat more by the
seeds than by inorganic objects of the same size. After they
re-expanded, the seeds were placed under favourable conditions on damp
sand; other seeds of the same lot being tried at the same time in the
same manner, and found to germinate well. Of the seven seeds which had
been exposed to the secretion, only three germinated; and one of the
three seedlings soon perished, the tip of its radicle being from the
first decayed, and the edges of its cotyledons of a dark brown colour;
so that altogether five out of the seven seeds ultimately perished.
Radish seeds (Raphanus sativus) of the previous year were placed on
three leaves, which became moderately inflected, and re-expanded on the
third or fourth day. Two of these seeds were transferred to damp sand;
only one germinated, and that very slowly. This seedling had an
extremely short, crooked, diseased, radicle, with no absorbent hairs;
and the cotyledons were oddly mottled with purple, with the edges
blackened and partly withered.
Cress seeds (Lepidum sativum) of the previous year were placed on four
leaves; two of these next morning were moderately and two strongly
inflected, and remained so for four, five, and even six days. Soon
after these seeds were placed on the leaves and had become damp, they
secreted in the usual manner a layer of tenacious mucus; and to
ascertain whether it was the absorption of this substance by the glands
which caused so much inflection, two seeds were put into water, and as
much of the mucus as possible scraped off. They were then placed on
leaves, which became very strongly inflected in the course of 3 hrs.,
and were still closely inflected on the third day; so that it evidently
was not the mucus which excited so [page 128] much inflection; on the
contrary, this served to a certain extent as a protection to the seeds.
Two of the six seeds germinated whilst still lying on the leaves, but
the seedlings, when transferred to damp sand, soon died; of the other
four seeds, only one germinated.
Two seeds of mustard (Sinapis nigra), two of celery (Apium
graveolens)—both of the previous year, two seeds well soaked of caraway
(Carum carui), and two of wheat, did not excite the leaves more than
inorganic objects often do. Five seeds, hardly ripe, of a buttercup
(Ranunculus), and two fresh seeds of Anemone nemorosa, induced only a
little more effect. On the other hand, four seeds, perhaps not quite
ripe, of Carex sylvatica caused the leaves on which they were placed to
be very strongly inflected; and these only began to re-expand on the
third day, one remaining inflected for seven days.
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