PROCEEDINGS OF THE PERTHSHIRE SOCIETY OP NATURAL SCIENCE. 
59 
or those of the daisy, of grasses, &c.), and a careful 
inspection may be needed to show their true nature. The 
readiest test is to cut through the suspected body, in 
which case, if it is a carpel, the seed will be found inside 
it. Such carpels (e.g., those mentioned above) are fre¬ 
quently small, but they are very rarely small enough to 
be carried about like dust, and equally rarely are rendered 
light by means of empty space in the walls of the carpels 
(e.g., in Myagrum and Valerianella species.) On the 
other hand, one-seeded carpels are often winged. The 
most rudimentary adaptation of this kind is seen in 
plants where the carpels are flattened as in Hcracleum, 
without being prolonged into a noticeable wing. From 
this stage all intermediate forms occur up to the bilateral 
wing of the elm and birch and the large unilateral 
wing of the maples. The ash-tree also has a long 
wing projecting beyond the seed - bearing portion. 
Similar winged carpels are found in many exotic plants 
of different genera and orders. A rarer form of vving 
occurs in Paliurus aculeatus, in which it encircles 
the carpel like an umbrella about half - way between 
the base and the apex. In all these cases the wing 
of the carpel is small in, or even absent from, the flower, 
becoming developed only as the ripening of the seed 
advances. 
Less frequently, very rarely indeed in British plants, 
the carpel becomes covered with a growth of long 
hairs, which form a float to support it in the air. In 
Dryas octopetala and in Clematis among native plants, and 
in various foreign species of different genera, the style, 
instead of falling off after the ovules are fertilised, 
increases much in size, and becomes converted into a float 
by the growth of long hairs all over ic. 
In many plants the outer envelopes of the flower, viz., 
corolla and calyx, or the flower-stalk or bract ( i.e ., the 
leaf between which and the stem the flower grows out), 
may become or may bear the adaptation for wind-carriage. 
The outer envelope or calyx is the part most frequently 
modified. If the calyx arises from the flower-stalk be¬ 
low the base of the ovary, and is free from the ovary, 
it may become much enlarged and bladdery, so as to 
surround the fruit, and to leave a large empty space 
between, rendering the whole body light. Such an 
arrangement may occur in plants with a calyx of coherent 
sepals (e.g., Trifolium fragiferum), or with a calyx of free 
sepals, e.g., Rumex. In some foreign plants (e.g., Gyro- 
carpus) two or more sepals may become much enlarged so 
as to form apparent wings; this may be the case in superior 
as well as in inferior calyces. 
In superior calyces, or th'ose which arise apparently 
from around the top of the ovary, the modifications 
met with are greater than in inferior calyces, and . are 
also more frequently met with ; but, as in them, be¬ 
come conspicuous only as the seeds ripen. In some 
plants the calyx spreads out like an umbrella, or like 
scales or plates, which buoy the fruit up, and render its 
fall slower. Most Compositce (dandelion, thistles, &c.) and 
some allied groups, e.g., Valeriana, have the calyx repre¬ 
sented by the pappus , a spreading crown of hairs arising 
(as in thistles) directly around the top of the ovary, or (as 
in the dandelion and goat’s beard) supported on a long beak 
that extends from the upper end of the ovary. These 
hairs may stand in one or in several rows, and may be 
simple or more or less branched. Their efficacy in floating 
the fruits is probably familiar to every one. In the 
cotton grasses (Eriophorum) we meet with a similar modi¬ 
fication in the floral envelopes. These consist of merely 
some slender hairs, which in the flower are quite small. 
As the seeds mature the hairs lengthen, and finally they 
become very conspicuous, forming large heads like masses 
of silky cotton, familiar to every one that has seen a 
Highland moor in summer. When the seed-like carpel 
breaks away the hairs are carried with it, and the whole 
floats away on the breeze. 
The corolla or inner floral envelope is so seldom modified 
apart from the outer that it needs no further comment 
here. 
In several of our native plants the flower-stalk bears hairs 
which elongate after the seeds are fertilised, and at last form 
relatively large tufts. Among the grasses Phragmites com¬ 
munis (reed) and Arena pubescens may be instanced. Typha 
latifolla also shows this arrangement. In such cases the 
flower-stalk breaks away, remaining attached to the ripe 
fruit. 
The lime-tree or linden (Tilia) gives an excellent ex¬ 
ample of the bract forming the wing. The flower-stalk 
(bearing several flowers, and therefore also several fruits) 
is adherent in part of its length to the long rather narrow 
bract. When the seeds are ripe the bract falls off with the 
fruits and flower-stalk, and is a very efficient means of 
conveying them to some distance before reaching the 
ground. In the hornbeam (Carpinus) and hop each fruit 
stands sessile in the axil of a small bract which falls off 
with it like a wing. In many grasses the glumes or bracts 
fall off with the fruit, and form imperfect floats, e.g., in 
Holcus , Plialaris, &c. 
Yet other modifications adapted for this mode of con¬ 
veyance of seeds are met with, but it would be tedious 
to dwell on them now, and, moreover, they rarely are 
found in Scottish plants. 
