173 



the horizontal, following some ridge of bark, or a holdfast root, 

 to its end, and then again turn downward. 



Some species of aroids produce one kind of root, some another, 

 and a few produce both. One species of Philodendron produces 

 a geotropic root from each alternate leaf, and, since the leaves 

 are two-ranked, all the roots appear on the same side of the stem, 

 and grow down the tree-trunk in a flat bundle because of their 

 strong thigmotropism. Several of the aroids begin producing 

 geotropic roots at an early stage, which soon aid materially in 

 water-conduction. The upper part of the stem,, supplied not 



Fig. 17. Lady Raffles' tomb on Canary Avenue, botanical garden, Buitenzorg, 

 Java.* 



only from below in the normal fashion, but also from the aerial 

 roots, is larger in diameter, and presents the phenomenon of a 

 stem enlarging upward. None of the Buitenzorg aroids, how- 

 ever, show this peculiarity as well as the Philippine Rhaphidio- 

 phoras. 



At the north end of Canary Avenue is a huge tangle of Gnetum 

 latifolium. The trunk is six inches in diameter at base, and 



* Lady Raffles was the wife of Sir Thomas Stamford Raffles, an EngUsh colo- 

 nial governor and administrator in Java and Sumatra (1781-1826). Rafflesia, one 

 of the most remarkable parasitic plants in the world, was described by Robert 

 Brown in 1821, from plants discovered in 1818 in Sumatra. The flowers are often 

 three feet across. — Ed. 



