62 



ANOMALOUS EXOGENOUS STEMS. 



Brazilian Sapindaoese, such as Paullinia pinnata (fig. 124:), Serj^nia 

 triternata and Selloviana, there is a centsal woody mass with from 

 three to ten small secondary ones round it. Each of the masses con- 

 tains true pith, derived either from the cortical cellular tissue, or 

 from the original medullary centre. Gaudichaud and Jussieu state 

 that around these separate collections of pith there is a medullary 

 sheath and spiral vessels. No annual rings have been detected in 

 the secondary masses, but medullary rays exist usually in their outer 

 portion (fig. 124). In these anomalous Sapindaoese, the central and 



Fig. 124. 



Fig. 126. Fig. 127. 



lateral woody masses are enclosed in a common bark, with a continuous 

 layer of liber. Some have supposed that the lateral masses are un- 

 developed branches united together under the bark ; but Treviranus 



Fig. 124. Homontal section of the stem of Paullinia pinnata, one of the Sapindaoese of 

 Brazil, showing numerons secondary woody masses surrounding a central one. Each of 

 the separate masses has pith, often excentric, with a medullary sheath, containing spiral 

 vessels, and a few medullary rays chiefly towards the circumference of the stem. Hg. 126. 

 Horizontal section of the stem of Bignonia capreolata, showing the crucial division of the 

 woody layers. Fig. 126. Horizontal section of stem of Heteropterys anomala, one of the 

 Braalian Malpighiacese, showing an irregularly lobed surface. The dots indicate porona 

 vessels. Fig. 127. Fragment of a stem of climbing species of Banisteria (B. scandens), 



showing the effects of compression. 



