xliv INTRODUCTION TO BOTANY. 



the second year, a new cluster springs up from the centre of 

 the former, and pushes outwards those that existed before. 

 Then the oldest begin to wither, to dry, and to fall off. But 

 their bases adhering intimately to the top of the root, are per- 

 sistent, and form, by their union, a solid ring, which becomes 

 the base of the stipe. A new central bud being developed 

 every year, the outer leaves of that which preceded it, fall off, 

 and their base, which is persistent, forms a new ring, which is 

 superadded to those that already existed. 



The stipe, instead of being formed of concentric layers like 

 the trunk of the dicotyledons, is composed of rings placed 

 above one another. 



Grafting. 



The union of grafts is effected by means of the cambium, 

 or proper juices of vegetables. This fluid substance serves as 

 a means of union between the graft and the stock, as in animals 

 the coagulable lymph is poured out between the edges of a 

 recent wound, which it unites and approximates. 



Slips. 



A slip will succeed with greater certainty, if we leave two 

 or three buds under ground. 



Height of Trees. 



The forests of South America, are, in general, full of fine, 

 lofty trees. Some plants are of very rapid growth. The 

 Agave Americana will grow nearly a foot every day. In 

 general, the greatest height attained by our forest trees, is from 

 one hundred and twenty, to one hundred and thirty feet. In 

 America, the palms, and other trees often exceed one hundred 

 and fifty feet. 



Thickness of Trees. 



The famous chestnut-tree of Mount Etna, is one hundred 

 and sixty feet in circumference. Of the baobabs in the Cape 

 De Verd islands, some were one hundred and twenty feet, in 

 circumference. In our own climate, there are oaks, &c. from 



