Febraary 27, 1890. J 
JOURNAL OF HORTICULTURE AND COTTAGE GARDENER. 
167 
E EMARKABLE plants have received a large share of attention 
lately, both in the horticultural and daily press ; writers in 
-some of the leading metropolitan organs devoting exhaustive, 
poetical, and imaginary articles to subjects that have been brought 
into prominent notice for some peculiar character. Few plants 
■can claim the honour of having a whole scientific report devoted to 
them, yet this has been accorded to “the Weather Plant,” con¬ 
cerning which notices have appeared in numberless papers, both 
here and on the continent. As Abrus precatorius this plant had 
long been a familiar occupant of botanic gardens, and its brilliant 
Ted black-tipped seeds are frequently seen in museums, either 
preserved as curiosities or employed in ornamental articles of native 
manufacture. An observer on the continent some time since, 
however, detected certain movements of the leaves that appeared 
to be connected with meteorological disturbances or changes, and 
•the attention of scientific men was especially directed to it. An 
important ultimate result of this was the institution at Kew of a 
•series of experiments, intended to test the reliability of the Abrus 
ss a natural meteorologist and prognosticator of the weather. It 
•must here be noted that the plant is a native of the West Indies, 
and though it succeeds in other tropical countries it was a severe 
test to expect it to act as a faithful indicator of the varying weather 
conditions of this climate. Possibly this may have disturbed the 
sensitive constitution of the plant sufficiently to account for the 
erratic nature of the record obtained, for though it was satisfac¬ 
torily proved that the weather influences the movement of the 
leaves to a certain extent, yet it does not appear that any definite 
rules can be laid down as to its behaviour. The prognostications 
of the meteorological office have frequently been the subject of 
satirical comments, but those of the Abrus are certainly less 
reliable, as far as can be judged from the admirable report so 
carefully prepared by Mr. Francis Oliver. 
The responsive action of plants, more particularly the leaves 
and flowers, to changes in the weather is not peculiar to one or 
two members of the vegetable kingdom, it is shared in some degree 
by a large number. Some of our most common wild plants are 
influenced considerably by light, heat, damp, and cold in the move¬ 
ments of their leaves. What is termed “ the sleep of plants ” is 
merely an effect due to the withdrawal of light or heat. Many 
observers have called attention to this, and to the varying mode in 
which the leaves fold up or are depressed in different species. It 
is more notable in compound leaves than in simple ones, and the 
position assumed by the leaflets in the Trefoils is familiar to 
everyone, each one folding on itself, and then the three draw up 
to the axis, being nearly upright. In species of Oxalis with 
similarly formed leaves, the leaflets droop downwards round the 
stalk. In pinnate leaves the pinnae are often depressed below the 
stalk, the under surfaces meeting. 
Flowers commonly expand in the morning and close in the 
evening, frequently remaining closed in dull, cold or wet weather. 
All such movements may therefore be considered as due to 
meteorological influences, though they have never yet been reduced 
to a system. It is true that with regard to the times at which 
flowers expand and close a kind of floral clock has been composed, 
but the times given for the various flowers can only be taken as 
approximative, and the divergence of an hour or two rather dis- 
No. 505.—VoL. XX., Thied Series. 
turbs the calculation of time by such means. All movements of 
plants in this way seem to depend upon so many conditions which 
are difficult to ascertain and cannot be accurately recorded, that 
it is too much to expect really definite results. 
Spontaneous movements of leaves, or those in response to 
some direct irritation, are more interesting and more regular. 
They have been subjected to close scientific study in the case of 
such as the Dionma and Droseras with surprising results, the 
carnivorous plants having enjoyed a notority far exceeding the 
“Weather Plant.” Even now they are inquired for by visitors 
to Kew with somewhat the same impressive interest that the lion 
house is sought in the Zoological Gardens. The infolding of the 
leaf lobes in the Dionasa when some substance is introduced is 
familiar to many now, as also is the rapid drooping of the Sensi¬ 
tive Plant leaves when touched. There is, however, an occupant 
of the stoves in some botanic gardens which displays a still 
more remarkable phenomenon in its leaves, and which is not 
nearly so well known. This is the Telegraph Plant, Desmodium 
gyrans, a member of the Leguminosie, a native of the East Indies, 
and by no means a novelty. Though Mr. Darwin and others 
have determined that most plants have a spontaneous motion in 
their growing stems and roots, these are so extremely gradual that 
they are not readily observed, and can only be tested by careful 
experiment. In the Desmodium, however, we have a spontaneous 
movement that is visible and strongly marked. The leaves consist 
of three leaflets, the centre one large, oblong, or elliptical, and at 
the base on each side is a small narrow leaflet, which possesses a 
peculiar property. When the plant is healthy and growing these 
leaflets rise alternately by a series of little jerks until they are 
nearly perpendicular, and then descend in a similar way, to resume 
their action when the other leaflet has gone through a similar pro¬ 
cess. This takes place without the application of any external 
stimulant beyond that afforded by light or heat ; the rapidity of 
the movement varies greatly, however, and in duU weather it is 
much reduced or ceases altogether, as it does when the plant 
becomes unhealthy or old. Sometimes the motion is confined to 
a few leaves, but it seems to depend chiefly on the age of the 
plant, the weather, or the conditions under which it is grown. In 
cold or a dry house it is much lessened, and does not continue 
so long. 
As regards the benefit plants themselves derive from these 
movements it is easy to understand that in the case of leaves fold 
ing up in dull weather or at night, the radiating surface is de¬ 
creased. Flowers are also protected by closing in cold or wet 
weather. The Dionsea and others having a similar character are 
believed to derive nitrogenous support from the flies and other 
insects they entrap. What advantage, however, can the Sensitive 
Mimosa or the Telegraph Plant derive from the motion of their 
leaves ? In a wild state we could imagine that the Mimosa is 
subject to a perpetual succession of alarms, and how can the 
drooping of its leaves protect or help it ? The restless action of 
the Desmodium leaflets might serve as an attraction, but if so it 
expends a considerable amount of energy in accomplishing what 
many other plants effect by means of their flowers in a quiet but 
much more certain manner. 
Another plant topic which has been treated rather fully, popu¬ 
larly, and practically in the papers lately is in connection with 
fragrant Ferns. Mr. W. Sowerby recently called attention to the 
fact that the fronds of Drynaria Willdenovi possess an agreeable 
haylike fragrance when drying, and immediately the writers were 
busy in the daily Press extolling its virtues and enlarging upon the 
subject generally. It is rather strange that this quality of the 
Drynaria (or Polypodium as it is designated in the “ Synopsis 
Filicum”) has not been recorded before, but fragrance is not 
expected in Ferns, and it is only those who are intimately ac¬ 
quainted with them that would be likely to detect their pecularities 
in this respect. Still, there are several Ferns which possess an un- 
No. 21G1.—VoL. LXXXII., Old Series. 
