278 VEGETABLE ORGANOGRAPHY. 



together, as in the Labiatae ; — 3d, when the stem pre- 

 sents distinct sides, the number of which corresponds to 

 that of the leaves ; such are the tetragonal branches of 

 Lagerstrcemia. When either of these three circum- 

 stances does not exist, the opposite or verticillate position 

 often suiFers exceptions, especially in the neighboui'hood 

 of flowers and at the origin of the branches. 



When the leaves are solitary on the same horizontal 

 plane, they are usually designated in botanical books 

 under the name of Scattered leaves, a very incorrect 

 term, for they are primitively an order quite as regular 

 as the preceding ; or of Alternate ones, an equally 

 incorrect term, since it designates a peculiar case of the 

 class, and that too which is the least frequent. 



We may distinguish in this class three principal dis- 

 positions, 1st. Leaves are said to be Alternate, in 

 the strict sense of the word, when they are disposed on 

 both sides of the branches in such a manner that the 

 third is found over the first, the fourth over the second, 

 &c. : among these alternate leaves we may distinguisl), 

 under the name of Distichous, those which are very 

 near together, and in two distinct rows. 2d. Leaves are 

 said to be Quincunx when they are arranged in a 

 simple spire, formed of five leaves, so that the sixth is 

 immediately over the first, the seventh over the second, 

 &c. ; this is a case of the most frequent occurrence — as, 

 for example, in the Pear, &c. 3d. The name of Spi- 

 rally ARRANGED Icavcs is reserved for all those which 

 have the spire formed of more than five leaves ; and here 

 we may reasonably distinguish the triple spires, such as 

 Pandanus or Draccena, in which each of the three spires 

 which surround the stem proceeds parallelly, and is com- 

 posed of from fifteen to twenty leaves ; — quintuple, sex- 

 tuple, &c., such as are found in different species of 

 Pinus, Euphorhium, &c. I have even found octuple 



