630 Staber: The anatomy of Sesban macrocarpa 



the principal ways that the tannin is found to occur in the plants. 

 For Sesban he states that it "has tannin-like latex vessels in 

 the external bark, under the phloem and among the pith." 

 The species under consideration, however, had tannin in the cor- 

 tex, in the leptome, and at the base of the bundles in the periphery 

 of the pith. In the preserved condition in which this plant was 

 studied, the cells containing this secretion appeared brown and 

 granular and were very noticeable under the microscope. The 

 test used for their determination was as follows : The sections 

 •were placed in concentrated aqueous solution of copper acetate for 

 three days, and then were treated with a 20 per cent, solution of 



w 



ferric acetate for a few minutes. The tannin present became green- 

 ish blue. In the cortex the tannin cells appeared without any. 

 particular order, but in the leptome long ducts had been formed 

 which were quite regularly placed, usually three to each bundle 

 (figure 3), The cross-walls of the ducts were missing, but slight 

 traces of their former position were observed in several places as 

 projections from the wall into the lumen. "^ Researches of Avetta, 

 Borzi, Baccarini, and Weyland show them to be syncytic in nature.f 

 The tannin cells, themselves, were cylindrical structures, slightly 

 constricted in the center, fitting end to end, averaging 28,16// long 



J 



and 1.76 /i wide in the old stem. 



The collenchyma forming a definite ring of three to five layers 

 was interrupted by an aerenchyraa (figure 4) of more or less 

 spongy tissue throughout the length of the stem. This was lack- 

 ing in the root. In Sesban actilata Pers. and Sesban marginata 

 Benth.,t however, a considerable aerenchyma was developed in 

 place of cork in the roots, which functioned as floating tissue. 



The cells forming the epidermis appeared polygonal in shape 

 when viewed from above. The stomata were of the usual type, 



F 



and were surrounded by four neighboring cells. The number of 

 stomata varied considerably ; in one strip of epidermis with an area 

 of 7.5 sq. mm. at a point 40 cm. from the base 6, only, were 

 found, while in a smaller piece of 4.7 sq. mm, at 14,7 cm,, 22 

 stomata were present. No hairs of any kind were present. 



*Meyen, Ueber Secretions-organe der Pflanzen, 47. Berlin, 1837. 

 fSolereder, Anatomic der Dicotyledonen, 294. 



i Scott & Wagner, Floating roots of Sesbania actdeata, Ann. Bot. i : 301-314 

 1888. Also Schenck, Aerenchym. Jahrb. Wiss. Bot. 20 : 554^557. 1889. 



