164 PEViir.v 



which, wl.emipe, shed their powder, called the pollen, on (he stigma, Cl 

 fertilize the llower. These anthers therefore must be carefully extracted be- 

 fore maturity, so 'as not to injure the stigma, which is tobe powdered with 

 the fertilizing: dust of another llower. A small pair of tweezers will be use- 

 ful for the first operation, and a soft brush of Camel's hair for the other. 

 Soon after the farina has been put upon the stigma, you will perceive the 

 seed vessel begin to swell gradually, and in the course of a fortnight you 

 will be in fresh danger of having your labour thrown away, lor in hot 

 weather the pods will often burst very suddenly, and scatter the seed in 

 all directions, In order to prevent this, tie a small piece of tape or gauze 

 about the pod, leaving it loose enough to allow room for the vessel to swell, 

 but making sure of catching the seed'whenever it is ejected, ^ow the seed in 

 a separate pot, with a distinct mark to it, that you may learn by the union, 

 of what plants to produce the finest flowers. Put them, when strong enough, 

 into a shady situation, and some of them will show bloom in the ensuing 

 autumn so as to enable you to form a judgment of their merits. And when 

 you have acquired more experience, forget not to furnish us with any useful 

 remarks that may occur to you, for the benefit of others." 



SCIENCE OF BOTANY. 



Continued from Puge 139. 



" In exogenous plants, the new matter being added externally, a bark or 

 covering' is necessary to protect it, when young and tender, from the action of 

 the atmosphere, and from external injury from other causes : hence an im- 

 portant office of the bark. In endogenous plants, the new matter, being 

 added internally, is provided with an excellent covering, formed of the main 

 substance of the plant, and has no need of a separate protecting integument. 

 " In spring there is found between the bark and the alburnum a viscid 

 gelatinous fluid called Cambium, which, it is supposed, is the principal S 

 in forming the new layers of wood and vi' bark. This fluid is composed of 

 the residue of the cambium of the preceding Beason, enriched and renewed 

 by the descending sap, and mixed with some of the secretions of the ve- 

 getable. 



" M. Mirbel and others are of opinion that the cambium annually forms a 

 new layer of alburnum and a new layer of bark, 'litis is the most simple 

 mode of formation, and probably that which hikes place. We know that the 

 cambium can repair the hark when it has been injured ; and, as the new 

 layers of wood and bark are formed where this fluid is found, it is not un- 

 reasonable to suppose that it acts an important part in this prt 



" M, Pu l'etit-Thouars advanced a singular theory, namely, that the suc- 

 cessive formation of woody layers is caused by the development ot buds, irem 

 which, in spring, issue numerous fibres, which descend in the cambium be- 

 tween the fiber and the alburnum. In gliding downwards they meet the fibres 

 which descend from other buds, and form a layer of greater or less thickness, 

 which soon becomes solid, and forms a layer of wood. 



" Each bud is regarded as a separate system of vegetation. The buds aie 

 considered so man', individuals placed upon a common stock, and elongat- 

 ing in two different ways — upwards, forming new stems and branches, leaves. 

 & c . — mid downwards, forming roots ; the descending fibres being the roots 

 which the buds put forth, and the cambium bearing the same relation to the 

 roots of the bud as the soil does to a germinating seed. M. Thenars con- 

 siders buds as analogous in structure and mode of development to the embryo 

 of the seed, which in germinating produces a young stem analogous to the 

 scion produced by the growth of a bud. He calls the latter, a faxed or ad- 



