438 [ASSEMBLT 



season advances, and by the middle of winter is condensed into & 

 compact ring of wood. 



These annual rings, visible in most plants when cut transverse- 

 ly, serve as a mark to determine their age. They decrease in 

 breadth as the plant advances to maturity, and are found to be 

 unequal in size throughout, varying as the season is favorable or 

 otherwise. 



The wood consists of two parts, the sap wood and the heart; 

 the former nourishes the bud. It is supposed that all the saccha- 

 rine matter of fruit trees is elaborated in the leaves of the pre- 

 ceding year, and deposited in the albumen, whence it is drawn 

 the lollowing spring for perfecting the flower and fruit. 



Air is indispensably necessary to all plants. It enters through 

 the cuticle. You may prove this by covering a plant with var- 

 nish, leaving the top exposed to air. During the first summer it 

 will inevitably perish. So it is with trees covered with moss, 

 Which always throw out weak, sickly and sparse leaves, produc- 

 ing a small quantity of inferior fruit. To the root a plant is in- 

 debted for its stability in the earth, and partial nourishment. All 

 roots are fibrous at their extremities, and furnished with a num- 

 ber of vessels for the purpose of conveying and circulating air 

 and the juices necessary to their growth. 



The leaves are essential to the existence of plants, as they will 

 perish if totally divested of them, and droop in proportion to the 

 quantity taken off. The upper and under surface of leaves are 

 covered with a inembrane, or their bark continued from the stalk. 



The flower consists of four parts, the corolla, the pistillum, the 

 calyx, and stamina. 



The calyx is usually of a green color, and is that which sur- 

 rounds and supports all the other parts of the -flower.* The co- 

 rolla is of various colors, and variously shaped in diSerent plants, 

 constituting the copspicuous part of the flower. Then there are 

 one or more petals. The stamina is the male part of the flower, 

 designed to prepare the pollen. Each stamen consists of two 

 parts ; a fine thread which supports the anthera, and the anthera 



