NOTES ON IDENTIFICATION OF TROPICAL WOOD 



491 



wide horizontally as the borders of the 

 pits themselves. The pits are uniformly 

 arranged over the entire surface of the 

 vessels. They are close together, uni- 

 form in size_, and hexagonal in outline. 

 The partitions between the pit cavities 

 are thin and delicate, resembling the 

 walls of honeycombs. The regularity 

 in the number and occurrence of pits 

 in vessel walls is rarely disturbed, but 

 there are places where the pits are not 

 fully developed ; here the pit canals are 

 present and the cavities are wanting. 

 The lenticular pit cavities and the slit- 

 like pit canals can best be seen in trans- 

 verse sections, especially if the section 

 be treated with a solution of iodine and 

 sulphuric acid or chloriodide of zinc. 

 The pit canals in the cross-walls of 

 abutting vessel segments cannot always 

 be clearly distinguished in longitudi- 

 nal sections. The canals themselves 

 are often mistaken for partition walls 

 between the adjoining pits. This error 

 may be avoided if one remembers that 

 pit canals always begin where the pit 

 cavities end. The lenticular pit cavities 

 are seen best in longitudinal sections. 

 Where the vessels are adjacent to wood 

 parenchyma, the pits within the walls 

 of the latter are the same as those in 

 pith ray cells, and those within the ves- 

 sel walls are bordered. The pits in the 

 cells of wood-parenchyma fibers and 

 pith rays are simple, and in vessels 

 they are bordered, resembling those in 

 tracheids of conifers. The pit cavi- 

 ties, however, are not shown so plainly 

 as they generally are in coniferous 

 woods. 



The cross walls of vessel segments 

 are now always in close union. The 

 portion between the abutting segments 

 is composed of a soluble substance. By 

 treating thin sections with potassium 

 chlorate and nitric acid, this substance 

 is dissolved, leaving the cross walls dis- 

 tinctly visible. The vessels are devel- 

 oped directly from wood parenchyma, 

 as may be determined from the inter- 



mediate forms which are very abund- 

 ant, especially where more than three 

 vessels are located side by side. Two 

 of these vessels are, then, as a rule, of 

 the usual diameter, and the others are 

 smaller. 



The structural characters of this 

 wood are like those of woods related to 

 Robinia, Gleditschia, Hcematoxylon 

 campechiannm L., Ccesalpinia echinata 

 Lam., etc., which are known as legumi- 

 nous woods. As was said, the occur- 

 rence of vessels as vessel cells and not 

 as vessel tubes is charactertistic of the 

 woods of this group. 



In conclusion, the question to be 

 solved is whether the regular alternat- 

 ing bands of wood fibers and wood 

 parenchyma correspond to annual in- 

 crement layers. The gross characters 

 showing that they do not coincide with 

 so-called annual rings have already 

 been given above. An anatomical in- 

 vestigation reveals the fact that there 

 are no elements present, either in the 

 parenchyma or prosenchyma layer, 

 which resemble intermediate forms in- 

 variably found in that part of the con- 

 centric zone where it changes gradually 

 from early to late wood. Nor is there a 

 known wood in which the early growth 

 is composed of tissue wholly diflferent 

 from that formed later. 



The facts determined thus far show 

 beyond doubt that it is a leguminous 

 wood. There is no analytical key based 

 on structural characters by means of 

 which it can be traced down to its 

 proper genus. Both the gross and 

 minute characters have been carefully 

 compared with those of authentic sam- 

 ples of Bozvdichia vir^^iloides, with 

 which they agree in every particular. 

 The generally accepted trade name for 

 this wood is Sebipira, which is also a 

 generic name given to it by Doctor von 

 Martins in 1828. It had been previ- 

 ouslv described, however, by Hum- 

 boldt, Bonpland. and Kunth as Boiv- 

 dichia vu\Q;iloides. 



