August 12, 1880. ] JOURNAL OF HORTICULTURE AND COTTAGE GARDENER. 
jEshna, specimens of which measure 4 inches across the wings. 
The larvae of all the dragonflies are voracious, and those that 
develope into the large species are proportionably large and 
strong, being able to master most aquatic insects, or even young 
fish. Occasionally, however, they are in their turn attacked by 
the water beetles and conquered. In the family Libellulidm the 
larvae is furnished with a singular apparatus, which has been 
called a mask ; it is an enlargement of the lower lip, and when 
not in action it folds over the mouth. When near the object it 
wishes to seize the larvae thrusts this forward, displaying what 
looks like a jointed bony tongue armed with a pair of nippers. 
The pupa of a dragonfly is as active as the larvae, or nearly so, 
until just upon the close of its aquatic life, when it crawls up the 
stalk of some water plant, and remains quiet waiting for the pupa 
shell to burst. When this event happens the fly shows much 
dexterity in escaping from its prison, and in drying its filmy 
wings, which are quite small at first, but expand as the fly some¬ 
how forces air into them from the body. The larvae of the Libel- 
lulidae are mostly stout, those of the Agrionidm, being of slender 
proportions, approach both in size and figure those of the Ephe- 
meridae or Mayflies. The Pirlidae or stoneflies represent a small 
group allied to the mayflies, wdth aquatic larvae, and perfect 
insects that are small-winged and of sluggish habit, therefore 
easily caught by those anglers who require them sometimes as 
bait.—C. 
FLORAL DEFENCES. 
The following is the substance of a lecture delivered to the mem¬ 
bers of the Liverpool Naturalists’ Field Club by the President, the 
Rev. Henry H. Higgins :— 
A market gardener wishing to improve his strain of Cucumbers 
frequently proceeds to select a flower from a Cucumber plant in some 
points finer than his own, and to place pollen from the new flower on 
the stigma of a flower belonging to the plant already in his frame. 
The flower matures, yielding a Cucumber apparently of the old sort. 
He, however, sows the seeds from this Cucumber, and from them he 
expects to grow plants bearing better Cucumbers. He is often suc¬ 
cessful. He finds that pollen from the new flower has done its work, 
and the gardener for his pains now has finer Cucumbers for seed and 
for the market. This is called cross-fertilisation (Xenogamy). 
What the gardener does for his Cucumbers Nature does for many 
of her flowers. She takes the pollen from a distant flower, and brings 
it home to the stigma of a flower of the same kind, but not growing 
on the same plant. The result is that the seeds are stronger than 
they would have been if the flower had been fertilised by pollen from 
another flower on the same stem. 
How does Nature bring the pollen from a distance ? Sometimes by 
the vdnd. On a sunny day towards the end of February tap with 
your walking stick a branch of Hazel bearing catkins—a cloud of 
yellow dust is carried away by the wind ; this is pollen, and some of 
it will fall on the tiny crimson flowers borne on the twigs of Hazel 
bushes far away, and they will produce fine clusters of ripe nuts 
when the proper time arrives. All catkin-bearing and cone-bearing 
trees, together with Grasses and Sedges, are fertilised chiefly by the 
wind. 
Tennyson refers to the profusion of pollen dust thrown off by the 
Yew tree in his “ Holy Grail,” near the commencement of the poem. 
“ 0 brother, I have seen this Yew tree smoke 
Spring after spring for half a hundred years.” 
Sometimes water conveys the pollen. Yallisneria (fig. 30) has flowers 
at the bottom of pools or slow streams 
in Italy. The pollen flowers when 
ripe are detached, and, rising to the 
surface, the pollen floats around. The 
pistil-bearing flowers are on stalks 
like corkscrews. When about to 
blossom the corkscrew stem straight¬ 
ens upwards and the pistil flower 
reaches the surface, where it meets 
with the pollen floating and is ferti¬ 
lised. After a few sunny days to 
ripen the seed the plant begins to 
twist up the corkscrew stem again, 
pulling the flower down; and the 
twisting goes on till the seed case is 
buried in the soil at the bottom of 
the stream, where the seeds can ger¬ 
minate and grow into fresh plants of 
Yallisneria. 
Some tropical flowers are fertilised 
by birds. A climbing plant, mentioned 
by Mr. Belt, in Central America 
(Marcgravia nepenthoides, fig. 31) has flowers suspended in an inverted 
umbel, as if they hung from the tips of an opened parasol. Where 
the handle of the parasol would be the plant forms a cluster of little 
pitchers containing honey. The honey attracts insects, and the 
insects humming birds, which, whilst feeding under the floral canopy, 
145 
dust their beautiful heads and crests with pollen, and then dart away 
to fertilise other blossoms. 
Most fi'equently the pollen is conveyed by insects. Many of us 
have seen in the course of a summer’s walk a humble bee banded 
with black and gold, with his muzzle deep down amongst the purple 
florets of a large Thistle head. He is helping himself and the plant 
at the same time—himself to the nectar which he loves, and the plant 
to the pollen of another like flower previously visited, thereby dixst- 
ing his limbs and coat with life germs of priceless value to the Thistle 
on which he is feeding. The insect and the plant may be varied in a 
thousand ways, still the object and the result of the visit are the 
same—the insect seeks the nectar, and the plant l-eceives the pollen, 
without which its seeds would remain unproductive. 
Not all insects are alike suited to fertilise every kind of plant. 
Some plants invite a butterfly, others a night-flying moth, whilst not 
a few are willing to be “ at home ” to a variety of flying visitors, the 
only stipulation being that they must be of suitable size, shape, and 
habits to bring with them pollen of the right kind, and to leave it in 
the right place. Now, other creatures besides these desirable guests 
love honey, especially ants, woodlice, plantlice, earwigs, and a whole 
host of small creeping things which prowl everywhere and are always 
hungry. These, as we shall see, are in many ways unfitted to ferti¬ 
lise most flowers. What, then, will be the fate of a flower exposed to 
such marauders and rifled of its precious nectar ? The gentle butter¬ 
fly or the helpful bee will not care to dally with the plundered 
blossom ; no pollen will be brought, and, so far as concerns progeny, 
its floral life will have been spent in vain. Hence the necessity for 
flowers to have guards suitable for keeping away unwelcome visitoi's 
—in other words, “ floral defences.” You will see at once how the 
subject differs from that of contrivances to attract and admit friendly 
visitors. The latter subject has been much longer before those of the 
public who are interested in such matters, and may be found fully 
treated in the works of Mr. Darwin, Sir John Lubbock, Dr. Ogle, 
H. and F. Muller, and others. 
Floral defences had been much less studied when, in 1878, first 
appeared an English translation of Dr. Kerner’s work on “Flowers 
and their Unbidden Guests.” To this work I am indebted for many 
of the facts which I have the pleasure of bringing before you on the 
present occasion. 
Perhaps the simplest of all modes of defence is seen in plants which 
turn their flowers away from the stem ; for the stem is the only road 
by which a creeping thing can reach a flower. Examples are very 
numerous. A common Snowdrop will serve for an illusti-ation. It 
must be evident that a creeping insect would find great difficulty in 
getting down the slender neck of the flower, and in crossing the 
incurved edges of the three white outer segments of the perianth, 
after which it would have to surmount the green-tipped segments, at 
the base of which on the inner side the honey lies. A bee has no 
such difficulty. Dr. Whew T ell speaks of the pensile position of the 
Snowdrop flower as conducing to its advantage. In his days no one 
had even suspected how. He calls attention to the fact that the 
nodding of the flower is occasioned by the force of gi-avity overcom¬ 
ing the elasticity of the flower stalk, and points out that if the earth 
were smaller than it is the flower would not droop so much, so that 
the whole mass of the earth from pole to pole is actually employed 
in keeping the flower of the Snowdrop pendulous on its graceful 
stalk. 
One of the most simple kinds of floral defence is used when the 
pollen, nectar, and pistil of a flower are shut up in a box with a 
spring lid, too strong to be raised by little impertinent wanderers, but 
easily lifted by a friend. Such a box you have often seen in the 
flower of the garden Snapdragon, Antirrhinum majus. No ant or 
other small insect can raise the lid, but when a lusty bee comes he 
shoves his head under the lid, and shortly almost his whole body 
disappears. Having finished to his satisfaction the little business on 
which he came he backs out, his legs and body dusted with the 
yellow pollen from the anthers ready to be carried to another flower. 
But why should an ant be unwelcome ? Because its polished 
