cold that has such an effect. Those who convey seeds from distant countries, should be instructed to keep them dry; for if they receive any damp sufficient to cause an attempt at vegetation, they necessarily die, because the process cannot, as they are situated, go on. It is usual with gardeners to keep melon and cucumber seeds for a few years, in order that the future plants may grow less luxuriantly, and be more abundant in blossoms and fruit. Dr. Darwin accounts for this from the damage which the lobes may receive from keeping, by which their power of nourishing the infant plant, at its first germination, is lessened, and it becomes stinted and dwarfish through its whole duration. QUESTIONS.-1. What takes place when a seed is committed to the ground? 2. What is said of the young root? 3. Of sea-weeds? 4. Of Dodder? 5. What are the two lobes called? 6. The germ? 7. How do the leaves of the germ assist the plant? 8. To what use is the farina of the lobes applied? 9. What are plants called that have only one lobe? 10. What is said of the preservation of the vital principle in seeds? 11. Why do gardeners sometimes keep melon and cucumber seeds for a few years? 12. How does Dr. Darwin account for this? LESSON 91. Roots, Stems, Buds, and Leaves. Rad'icle, the minute branch of a root. Physiology, the doctrine of the constitution of the works of nature. Perspire', to give out moisture. Absorb', to take in moisture. THE root of a plant consists of two parts, the body of the root, and the fibre. The latter only is essential, being the part which imbibes nourishment. Roots are either of annual, biennial, or perennial duration. The first belong to plants which live only one year, or rather one summer, as barley; the second to such as are produced one season, and, living through the ensuing winter, produce flowers and fruit the following summer, as winter-rye and wheat; and the third to those which live and blossom through many succeeding seasons to an indefinite period, as trees and many herbaceous plants. Botanists distinguish several different kinds of roots, which are necessary to be known, not only for botanical purposes, but as being of great importance in agriculture and gardening. Barren and thin soils are best suited to the wide spreading roots, which creep extensively on the surface; dry and sandy plains are adapted to those which penetrate deep for nourishment, and are supplied with bulbs for its preservation, or with downy radicles for its abundant absorption. Linnæus enumerates seven kinds of trunks, stems, or stalks of vegetables. These are necessary to be known for botanical distinctions, though some are more important than others. About midsummer the progress of vegetation seems to be suspended, and for several days the vital energies of the tree are exerted in the formation of buds. We no longer observe the vigorous growth of spring, but if we examine the young branches, we shall find the newly formed buds at the base of the leaf-stalk, immediately above the place of their insertion. After the fall of the leaves they are more conspicuous, and during the winter we may perceive a gradual enlargement, corresponding to the developement of the tender germs which they enclose. Plants, as is well known, may be propagated by buds, and in that sense each bud is a separate being, or a young plant in itself; but such propagation is only the extension of an individual, and not à re-production of the species, as by seed. Leaves are eminently ornamental to plants from their pleas ing colour, and the infinite variety as well as elegance of their forms. Their different situations, insertions, forms, and surfaces, which are of the greatest possible use in systematical botany, cannot here be described. A knowledge of their real use with regard to the plant is a curious branch of vegetable physiology. That leaves give out moisture, or are organs of insensible perspiration, is proved by the simple experiment of gathering the leafy branch of a tree, and immediately stopping the wound at its base with wax to prevent the effusion of moisture in that direction. In a very short time the leaves droop, wither, and are dried up. If the same branch, partly faded, though not dead, be placed in a very damp cellar, or immersed in water, the leaves revive, by which their power of absorption is also proved. A knowledge of the perspiring and absorbing power of leaves is often of great practical importance. It teaches us that plants droop, in consequence of the excess of the former, and are to be revived by diminishing their discharge, or increasing their absorption. The former is accomplished by confining the air around them, and the latter by sprinkling water over the leaves; and when plants have recently been removed, such management is frequently required. Air is not less essential to the healthy existence of animals than of plants. One great use of leaves is to perform in some measure, the same office for the support of vegetable life, that the lungs of animals do for the support of animal life. Light has a very powerful effect upon plants, and the green colour of leaves is so much owing to it, that plants raised in darkness are of a sickly white Light acts beneficially upon the upper surface of leaves, and hurtfully upon the under side; hence the former is always turned towards the light, in whatever situation the plant may be placed. A great number of leaves follow the sun in its course, and a familiar instance of this is a clover-field. The leaves of some plants, when the light is withdrawn, fold over each other, or droop as if dying; and this is called by Linnæus the sleep of plants. Some leaves display an extraordinary sensibility to the touch of any extraneous body, or to any sudden concussion, as those of the sensitive plant. An impression made, in the most gentle manner, upon one of its leaflets, is communicated in succession to all of them, evincing an exquisite irritability. The moving plant of India exhibits such powers as to excite the astonishment of every beholder. its motion be impeded, no sooner does it regain its liberty than its operations are renewed with increased activity, as if it were necessary to redeem the time which it had lost. Its winged leaves seem to disdain to rest, and to exhibit a most astonishing example of industry. If QUESTIONS.-1. What are the two parts of the root of a plant? 2. How are roots divided with regard to their duration? 3. Give the examples. 4. What is said of buds? 5. How is it proved that leaves are organs of perspiration, and of absorption? 6. What office do leaves perform for plants? 7. What is the effect of light upon plants, and leaves? 8. What is said of the sensitive plant? 9. Of the moving plant of India? 10. Describe the several kinds of Roots, (see Appendix.) 11. What is said of the root of common herds grass? 12. What are the seven kinds of trunks or stems? 13. What are the several kinds of appendages to a plant? 14. What are the several kinds of Inflorescence? FLOWER AND FRUIT. 205 LESSON 92. Flower and Fruit. Filiform, thread like, or very slender. Ves'icle, a small cuticle, filled or inflated, or a little bladder. In colour these, and those delight the smell; CowPER. LINNEUS classed the flower and fruit together, and defined them to be a temporary part of vegetables, destined for the reproduction of the species, terminating the old individual and beginning the new. These constitute the reproductive organs, by which the species have been hitherto preserved from extinction, and by which alone they will be renewed, so long as seed time and harvest continue. There are seven of these organs, some of which are essential to the very nature of flower or fruit, others not so indispensably necessary, and therefore not universal. The student, who wishes to gain an adequate idea of these organs, should dissect different flowers, and bestow upon each part a separate examination. He will find externally the calyx or flowercup, usually of a green colour, and often wanting; the corolla, or as it is sometimes termed the blossom, assuming various shades of colour, exhibiting a more delicate texture than the preceding, and like it sometimes wanting; the stamens, which are filiform organs arranged interior to the corolla, and are never wanting; the pistils, arising from the centre of the flower, containing the rudiments of the fruit, and of course essential; the seed-vessel, of a pulpy, woody, or leathery texture, enclosing the seeds, but wanting in many plants; the seed, the perfecting of which is the sole end of all the other parts; and the receptacle, or base, which is the point of connexion, and must necessarily be present in some form or other. The corolla constitutes the chief beauty of a flower, and includes two parts, the Petal and the Nectary. The former 206 FLOWER AND FRUIT. is either simple, as in the primrose and bell shaped flowers, in which case the corolla is said to be monopet'alous; or compound, as in the rose, in which it is polypet'alous. The whole use and physiology of the corolla have not yet been fully explained. The nectary contains or secretes honey; and there can be no doubt that the sole use of the honey with respect to the plant is to tempt insects, who in procuring it fertilize the flower, by disturbing the dust of the stamens, and even carry that substance from the barren to the fertile blossoms. A stamen commonly consists of two parts, the Filament and Anther, the former being merely what supports the latter, which is the only essential part. The anther is generally of a membranous texture, consisting of two cells or cavities. It contains the Pollen, or Dust, which is thrown out chiefly in warm dry weather, when the coat of the anther contracts and bursts. The Pollen, though to the naked eye a fine powder, and light enough to be wafted along by the air, is so curiously formed, and so various in different plants, as to be an interesting and popular object for the microscope. Each grain of it is a round or angular, rough or smooth vesicle, which remains entire till it meets with any moisture, being contrary in this respect to the nature of the anther; then it bursts with great force, discharging a most subtile vapour. The Pistil consists of three parts: the Germen, or rudiment of the young fruit and seed; the style, various in bagth and thickness, sometimes altogether wanting, and when present serving merely to elevate the third part, which is called the Stigma. This last is indispensable. It is very generally downy, and always more or less moist. The moisture is designed for the reception of the pollen, which explodes on meeting with it, and hence the seeds are fertilized and rendered capable of ripening, which they would not otherwise be, though in many plants fully formed. The ways in which insects serve the purpose of perfecting the seeds in plants are innumerable. These active little beings are peculiarly busy about flowers in bright sunny weather, when every blossom is expanded, the pollen in perfection, and all the powers of vegetation in their greatest vigour. Then we see the rough sides and legs of the bee, laden with the golden dust which it shakes off, and collects anew, in its visits to the honeyed stores inviting it on every |