SIR H. DAVYS AGRTCULTITRAL CHEMISTRY. 



107 



from a tree in the spring it uniformly 

 dies, and when many of the leaves of 

 forest trees are injured by blasts, the 

 trees always become stagheaded and un- 

 healthy. 



The leaves are necessary for the exist- 

 ence of the individual tree, the flowers 

 for the continuance of the species. Of all 

 tile parts of the plants they are the most 

 refined, the most beautiful in their struc- 

 ture and appear as the master-work of 

 nature in the vegetable kingdom. The 

 elegance of their lints, the variety of their 

 forms, the delicacy of their organization, 

 and the adaptation of their parts, are all 

 calculated to awaken our curiosity, and 

 excite our admiration. 



In the flower there are to be observed, 

 1st, the calyx, ov green membranous part 

 forming tlie support of the colored floral 

 leaves. This is vascular, and agrees with 

 the common leaf in its texture and organi- 

 zation; it defends, supports, and nourishes 

 the more perfect parts, 2d, the corolla, 

 which consists either of a single piece, 

 when it is called monopetalous, or of 

 jrtany pieces, when it is called polypetal- 

 ous. It is usually very vivid in its color, 

 is filled with an almost infinite variety of 

 small tubes of the porous kind; it incloses 

 and defends the essential parts in the in- 

 terior, and supplies the juices of the sap 

 to them. These parts are, 3d, the stamens 

 and the pistils. 



The essential part of the stamens are 

 the summit or anthers, which are usually 

 circular and of a highly vascular texture, 

 and covered with a fine dust called the 

 pollen. 



The pistil is cylindrical, and surmount- 

 ed by the style; the top of which is 

 generally round and protuberant. 



In the pistil, when it is examined by 

 the microscope, congeries of spherical 

 forms may usually be perceived, which 

 seem to be the bases of future seeds. 



It is upon the arrangement of the 

 stamens and the pistils, that the Linnaean 

 classification is founded. The numbers 

 of the stamens and pistils in the same 

 flower, their arrangements, or their divi- 

 sion in different flowers, are the circum- 

 stances which guided the Swedish philo- 

 sopher, and enabled him to form a system 

 admirably adapted to assist the memory, 



and render botany of easy acquisition; and 

 which, though it does not always associate 

 together the plants most analogous to each 

 other in their general characters, is yet so 

 ingeniously contrived as to denote all the 

 analogies of their most essential parts. 



The pistil is the organ which contains 

 the rudiments of the seed, but the seed 

 is never formed as a reproductive germ, 

 without the influence of the pollen, or 

 dust on the anthers. 



This mysterious impression is neces- 

 sary to the continued succession of the 

 different vegetable tiibes. It is a feature 

 which extends the resemblances of the 

 different orders of beings, and establishes, 

 on a great scale, the beautiful analogy of 

 nature. 



The ancients had observed, that different 

 date trees, bore different flowers, and that 

 those trees producing flowers which con- 

 tained pistils bore no fruit, unless in the 

 immediate vicinity of such trees as pro- 

 duced flowers containing stamens. This 

 long established fact strongly impressed 

 the mind of Malpighi, who ascertained 

 several analogous facts with regard to 

 other vegetables. Grew, however, was 

 the first person who attempted to general- 

 ize upon them, and much just reasoning 

 upon the subject may be found in his 

 works. Linnaeus gave a scientific and 

 distinct form to that which Grew had 

 only generally observed, and has the 

 glory of establishing what has been called 

 the sexual system, upon the basis of 

 minute observations and accurate ex- 

 periments. 



The seed, the last production of vigor- 

 ous vegetation, is wonderfully diversified 

 in form. Being of the highest importance 

 to the resources of nature, it is defended 

 above all other jiarts of the plant; by soft 

 pulpy substances, as in the esculent fruits, 

 by thick membranes, as in the lugumin- 

 ous vegetables, and by hard shells, or a 

 thick epidermis, as in the palms and 

 grasses. In every seed there is to be 

 distinguished, 1st, the organ of nourish- 

 ment; 2d, the nascent plant, or the plume; 

 3d, the nascent root, or the radicle. 



In the common garden bean, the organ 

 of nourishment is divided into two lobes 

 called cotyledons; the plume is the small 

 white point between the upper part of the 



