73b LECTURE i.viir. 



kind occurs in animal life, Avliere a tooth has been transplanted intb tht 

 socket of another, or where the spur of a cock has been inserted into his comb. 



Plants have their natural periods of life, either of a few days, as in the case 

 of some of the fungi, of a year, of a few years, or of many centuries. They 

 have also their diseases ; they are often infested by insects, as in the gall of 

 the oak, and the woodruff of the rose, or by animalcules of a still lower order, 

 which are either the causes of the smut of corn, or constant attendants on it. 

 From unnatural and too luxuriant culture, they become sterile, and produce 

 double flowers instead of fruits and seeds. When deprived of sufficient mois- 

 ture, or nipped by frost, their leaves and branches often die^ and if the 

 plants recover their vigour, a separation is affected by a natural process, re- 

 sembling the sloughing of decayed parts of animals: but when the whole 

 plant sinks, the dead leaves continue to adhere to it. The annual fall of 

 leaves in autumn appears to be a natural separation nearly of the same kind, 

 which takes place when the leaves are no longer wanted; the growth of the 

 plant being discontinued, and their functions being no longer required. 



Succulent plants generally die when the cuticle is removed, but not all 

 other plants. The air appears to be injurious to vegetables where it is not 

 natural; hence arises the benefit of Mr. Forsyth's method of completely ex- 

 cluding the air from the wounded parts of trees, by means of which their 

 losses are often in great measure repaired, and they acquire new strength and 

 vigour. Sometimes a diminution of the magnitude of a tree immediately in- 

 creases its fertihty ; its force being more concentrated, by lopping off its use- 

 less branches and leaves, it produces a larger quantity of fruit, with the juices 

 which would have been expended in their nourishment. 



The Linnean system of vegetables is confessedly rather an artificial than a 

 natural one; but it is extremely well adapted for practice, and its universal 

 adoption has been productive of the most important improvements in the sci- 

 ence of botany. Of the 24 classes into which Linn^> has divided the vegeta- 

 ble kingdom, 23 are distinguished by the forms of the flowers and fruit, and 

 the 24th by the want of a regular florescence. The first 10 are named from 

 monandria, in order, to decandria; then follow dodecandria; icosandria, and 

 polyandria; the names expressing the niimber of the stamina, or filaments, 

 surrounding the seed vessel; and the orders are deduced in a similar manner 



