EXCURSION ON THE RIO NEGRO. 



335 



plants throughout the whole vegetable kingdom are ar- 

 ranged ; laws now recognized by the most advanced botan- 

 ists of the day, and designated by them as Phyllotaxis. The 

 simplest arrangement in these mathematics of the vegetable 

 world is that of the grasses, in which the leaves are placed 

 alternately on opposite sides of the stem, thus dividing the 

 space around it in equal halves. As the stem of the grasses 

 elongates, these pairs of leaves are found scattered along its 

 length ; and it is only in ears or spikes of some genera that 

 we find them growing so compactly on the axis as to form a 



F:in R;icr:\!>:i ( fF.noc.irpu* 



close head. Of this law of growth the palm known as the 

 Baccaba of Para ((Enocarpus distychius) is an admirable 



