774 BOTANY AND PHARMACOGNOSY. 



** Pollen Grains Few. 

 t Trachece Present. 



175. CUSSO. Light brown (Figs. 150, 243) ; calcium oxal- 

 ate in rosette aggregates, about 20 ix in diameter ; non-glandular 

 hairs i-celled, curved, thick-walled, 0.2 to 0.5 mm. long; gland- 

 ular hairs with 2- or 3-celled stalk, glandular head unicellular or 

 consisting of one or two pairs of cells ; trachese spiral, scalariform, 

 or with bordered pores ; sclerenchymatous fibers long, thick- 

 walled, strongly lignified, with numerous simple oblique pores; 

 parenchyma of pith more or less lignified and with simple pores ; 

 pollen grains few, somewhat ellipsoidal, 25 to 40 jx in diameter, 

 with three pores. 



ft Trachea Wanting. 



176. VIBURNUM OPULUS. (See No. 179.) 



177. VIBURNUM PRUNIFOLIUM. Dark brown; cal- 

 cium oxalate in rosette aggregates and few monoclinic prisms 15 

 to 35 IX in diameter; crystal fibers with rosette aggregates and 

 occasional monoclinic prisms of calcium oxalate ; stone cells large, 

 numerous, irregular, thick-walled and with a few canals ; bast 

 fibers comparatively few, lignified. The barks of other species of 

 Viburnum are frequently substituted for V. priinifolium. 



P Calcium Oxalate in Monoclinic Prisms. 

 I. Numerous Seeds. 



178. VANILLA. Blackish-brown (Figs. 256; 285, G; 313) ; 

 calcium oxalate in monoclinic prisms 7 to 35 /a in diameter or in 

 raphides about 0.4 mm. long; occasional unicellular glandular 

 papillae with rounded apex and containing oil-like globules of a 

 balsam ; sclerenchymatous fibers more or less thick-walled, 

 strongly lignified and with numerous oval pores ; tracheae with 

 spiral or reticulate thickenings ; minute, black, ovoid seeds about 

 0.5 mm. in diameter, the structure being apparent only after boil- 

 ing with chloral solution or solutions of the alkalies. The powder 

 on treatment with a phloroglucin solution and sulphuric acid 

 assumes a deep red color, due to the presence of vanillin. 



