Senccio pi'CBcox, D. C, from Mexico. 39 



bei Kleinia artiadata), und die Wasscrmengen, welche in dem 

 Vegetationskorper einer solchen Pflanze aufgespeichert sind, 

 sind teilweise recht betrachtliche." 



Histology of the Root. — The smallest roots (^-inch diameter) 

 show about twelve concentric rows of cork with the outer 

 wall of each cell somewhat bowed. The cortex consists of 

 at least six concentric rows of rounded parenchyma cells, 

 which when stained with Kleinenberg's alcoholic haematoxylon 

 take a deep purple color. The central stele is diarchic, and 

 differs little from that of an ordinary dicotyledonous root. 

 The older roots show considerably more cork, and the outer 

 layers have begun to exfoliate. Such roots soon exhibit the 

 modifications, which take place in the increased thickening of 

 dicotyledonous roots, namely the gradual shifting of the radially 

 arranged phloem until it occupies an outside position with ref- 

 erence to the wood. When this growth is completed, normal 

 increase proceeds as in the stem. Balsamic reservoirs are seen 

 in two positions in the exocortex and endocortex of the roots. 



Histology of the Stem. — The cork ((T Text Fig.), in com- 

 parison to the diameter of the stem, is not so plentiful as in 

 the roots. It is formed from a phellogenetic layer just out- 

 side of the green phelloderm. The green portion of the cortex 

 shows quite large, light green chlorophyll grains. The spaces 

 in the cortex, which are formed lysigenously, contain a fluid 

 which, subjected to the following tests, seems to indicate that 

 we have to deal with a balsam, rather than a true resin. Abso- 

 lute alcohol dissolves the exudate without a sediment. Tur- 

 pentine dissolves the clear, amber-like substance with a slight 

 granular sediment. Ether dissolves it without a sediment. 

 The exudation is insoluble in cold, but soluble in hot, potash, 

 leaving a slight cloudy precipitate. Aqueous solution of 

 acetate of copper was used upon several sections, exposed to 

 its action for five or six days, without obtaining the emerald- 

 green resin reaction. The smell, suggesting the presence of a 

 volatile oil seems also to point to the exudate, being a balsam. 



