130 Mr. A. Henfrey on the Progress of Physiological Botany : 



ley*, Gaudichaud t and Schleiden J. Here the general mass of 

 the wood is interrupted by plates of a diflferent substance which 

 pass in from the circumference to the centre, which substance, if 

 it be wood, is of a distinct kind from the rest ; these plates cor- 

 respond to each other on the opposite sides of the stem. Gau- 

 dichaud says that the Bignoniacea in Guayaquil have originally 

 tour of these plates, next eight, then sixteen, and probably after- 

 wards thirty-two -, but he never saw this in the plateaux of 

 Brazil. 



Analogous but less regular divisions of the wood occur to a 

 certain extent in old stems of Bignonia capreolata, but here only 

 four plates exist in stems even two inches in diameter. In a 

 stem of a Bignonia collected in Columbia by Karsten (marked 

 No. 33) there are eight such divisions, of which four are not so 

 broad as the other four, and they correspond to each other ex- 

 actly on opposite sides of the stem. Jussieu found four in B. 

 Unguis Cati and B. grandiflora ; in a Bignoniaceous plant from 

 Peru eight, with the traces of the commencement of a duphca- 

 tion of them, which would thus have made sixteen. 



Their intimate structure exhibits chiefly fibrous tubes, agree- 

 ing with those of liber, but in B. capreolata the author found 

 vessels. The former are arranged in transverse rows with thin 

 layers of cellular tissue interposed ', an organization similar to 

 that of liber. They never reach quite to the pith, the wood im- 

 mediately surrounding this is therefore undivided, and they are 

 only firmly united to the true wood at those points where they 

 terminate intei'nally. A recently gathered leafy shoot of B. ca- 

 preolata about a line and a half in diameter, exhibited the first 

 trace of these four introversions of the liber. Where each of 

 these originated in the bark there was a fibrous bundle like the 

 others, but much larger. There were four of these chief bundles, 

 and they had their origin in the petiole like the woody bodies of 

 the bark in Calycanthus and Paullinia. It appears therefore that 

 continual additions are made to the liber on the inside of these 

 bundles as the wood of the stem increases in diameter, and con- 

 sequently, no formation of true wood occumng at these points, 

 cavities would result, but that the liber bundles grow inward and 

 fill them up. 



Comparing these last-mentioned forms of ligneous structure 

 with that of Calycanthus, of certain Malpighiacece and Sapindacea, 

 the distinction is observed, that in the Bignoniacea the fibrous 

 substance, separated from the chief mass of the wood, does not 

 develope outside the latter, but in and with it, at the same time 



* Introduct. to Botanj', fig. 38. 



t Fecherch. &c. t. 14. fig. 4, t. 18. figs. 4-10. 



X Grundziige, &c. 2nd ed. fig. 146-148. 



