ROWLEE: SYNOPSIS OF THE GENUS OCHROMA 159 



Colombia and this was described by Willdenow under the name 

 Ochroma tomcntosa. This second species has never been found 

 outside the region where Humboldt collected it. Swartz's type 

 locality is "Jamaica, Hispaniola," but specimens from South 

 America, Central America, and the West Indies have been 

 universally referred to O. lagopus. These two species are the 

 only ones recognized in botanical literature at the present time. 



Ochroma is confined to tropical America. Its nearest relative 

 in the eastern hemisphere is the baobab tree. It is a relative of 

 the "ceiba" {Bumbax) and "quipo" {Cavanillcsia), of tropical 

 America. 



The species of this genus most frequently occur in the low- 

 lands and foothills, though rarely, if ever, where the soil is at all 

 affected by brackish or salt water. They have not been dis- 

 covered in the higher altitudes, that is, at more than i,ooo 

 meters above sea level. 



Balsa is usually a second-growth tree, though it does occur 

 as an isolated tree in the primeval forest. It appears promptly 

 and abundantly where clearings have been made by natural 

 agencies, such as floods and fires, or by human cultivations. In 

 this respect it might properly be called a tree "weed." The 

 natural seeding in some places produces such an abundance of 

 young plants as to suggest weeds in a neglected garden. The 

 tree's growth is very rapid. During the first five or six years 

 of its life it may attain a trunk diameter of 60 to 75 cm., an 

 average increase in thickness of 12 or 13 cm. per year. It also 

 grows very rapidly in height, often attaining under favorable 

 conditions 16 or 20 meters in five or six years. This gives it a 

 place among the most rapidly growing trees known, if indeed 

 it is not the most rapid of all. 



In the natural state, the wood is very perishable. One rarely 

 sees the remains of trees of balsa in the tropical forests. They 

 decay with apparently the same rapidity as a cotton fabric; the 

 wood absorbs moisture readily and shrinks and warps badly. 

 This is due undoubtedly to the feeble lignification of the cell 

 walls and to the lack of aseptic properties such as the timber of 

 oak and pine possess. It was only when the engineers of the 



