170 



KNOWLEDGE. 



[August, 1901. 



direct, the aLtentiou of iiiscc-ts, mil lo t liBmselves, but. 

 to l-he adjoining perfect tlowers, which are awaiting 

 fertilization. This plant, in fact, keeps an advertising 

 staff, whose sole duty is to draw attention to the wares 

 offered by the comparatively inconspicuous noimal 

 ilowers. In several species of Knapweed, notably in the 

 handsome Cevfuuren Srabjom, a similar division of 

 labour is to be found. In other plants the leaves are 

 pressed into the service as advertising agents. A notable 

 example is furnished by the little Dwai-f Cornel, Coiiius 

 xuecicci, found in mountain pastures. The umbel of 

 small dark pui-ple flowers is set in four conspicuous 

 white petal-like leaves, which serve the purpose of the 

 showy corollas of so many eutomophilous flowers. In 

 many of the Composite^, which form so large an order, 

 this differentiation of flowers exists in a marked degree. 

 Of the Knapweeds we have already spoken. In the 

 Daisy and many of its allies, the majority of the flowers 

 are small, with a yellow regular corolla, enclosing male 

 and female organs. The mass of yellow flowers is sur- 

 rounded by a ring of flowers possessing female organs 

 only, in which the corolla is white, and is prolonged on 

 the free side into a conspicuous limb. In the allied 

 Dandelion group, the corollas of all the flowers are en- 

 larged on one side in this way, and point outwards from 

 the centre. The accompanying photograph illustrates 

 characteristic species of our two largest orders of 

 grouped flowers — the Umbellifers and Composites. 



KiG. 1. — Wild Angelica ami Ox-i-_vi- Diii^its. [Iliistraliiif; liio 



foiispipiious <-ffi>ct produced by the gi'oupin;; of uuiiiermis 



small ilowevs. 



When flowering is over, and by means of insects or 

 the wind or other agencies fertilization ha.s been effected, 

 thci-c follows a period unintc>resting to the casual 



observe)-, but of the greatest importance to the plants — 

 the period of tlie growth and development of the fruit 

 — that is, of the seed and its envelopes. In many cases, 

 beyond the falling off or witheriiig of the no longer 

 useful showy parts of the flower, no external change is 

 noticeable ; but in many plants this is a period of 

 vigorous growth — as in the Peas and Beans and many 

 Cruciferous plants, and in plants with fleshy fruits, such 

 as the Apple and Plum. The corolla, when its work of 

 advertisement is done, usually falls ; sometimes, as in 

 our common Heaths, it remains di-y and withered, and 

 no doubt serves to protect the ripening fruit. The outer 

 whorl, or calyx, is more persistent, and very frequently 

 wi-aps about the young fruit, often growing as it grows, 

 ?nd forming a protective envelope. In many plants 

 interesting movements may be noted between the periods 

 of flowering and fruiting. In the numerous Pondweeds, 

 for instance, which grow submerged or floating in wat«r, 

 the flowers are wind-fertilized, and during the period of 

 blossoming the spikes of flower stand up erect above the 

 water owing to curving of the flower-stem. When flower- 

 ing is over, a reverse ciu-vature submerges them, and the 

 fruit is ripened below the surface, where it is less liable 

 to misadventure from wind and wave. In the Water- 

 Crowfoots, which are insect.-fertilized, tlie same move- 

 ment may be observed. A reverse movement is notice- 

 able in various insect^fertilized land flowers. The buds 

 of the Wild Hyacinth, Columbine, St. Dabeoc's Heath, 

 are erect, but on expanding the bell-like flowers hang 

 mouth downward, thus protecting the delicate essential 

 organs from rain and cold. W^lien flowering is over, the 

 erect attitude is resumed, and the fruit ripens in that 

 position. The Meadow Crane's-bill and Wood Crane's- 

 bill are closely allied species, and much resemble each 

 other in general appearance ; but while the fruit of the 

 one stands erect, in the other each fruit is pointed down- 

 ward. What subtle difference between the mode of life 

 or surroundings of the two plants has produced this 

 change of posture since their derivation from a common 

 ancestor, it is not easy to conjecture. 



And now, as the result of this long life-histoiy, the 

 seed lies mature and ripe within the seed vessel — be it 

 a leathery pod, or a woody box, or a juicy berry or 

 pome ; and the seed vessel is ready to separate from the 

 parent stem, or to open and allow the seeds to escape. 

 This is a critical time in the plant's history ; quite as 

 important as the period of flowering. On the successful 

 sowing of the precious seed depends the life of the 

 succeeding generation. What wonder then if we find, in 

 connection with seed-dispersal, ai-rangements as elaborate 

 and contrivances as ingenious as those which we have 

 glanced at in connection with flower-fertilization. 



In comparatively few cases do the seeds merely fall 

 to the ground beside the parent plant, with apparently 

 no means of further dispersal : the Buttercups and Wood 

 Anemone appear to Iseloug to this category. More 

 frequently advantage is taken of some motive agent, 

 which can assist the seed to a wider dissemination, that 

 it may grow up clear of the impending shade of the 

 parent, and of the exhausted soil which surrounds it, 

 and by seeking fresh woods and pastures new, colonize 

 the country and hold its own in the rough-and-tumble 

 of overcrowded vegetation. These motive agencies are 

 furnished by wind and water — notably by the former — 

 and by animals. The simplest cases of wind-dispersal 

 we see in the swaying of the herbs and trees as the 

 breeze rustles through the woods and meadows. In 

 many plants the ripe fruit or seeds lie in cup-shaped 

 or saucer-shaped receptacles, out of which they would 



