392 PROCEEDINGS OF THE ACADEMY OF [1898. 



97. Zinnia pauciflora Linn. Sp. PL ed. II, 1,269 ; Lam. 111., t. 685, f. 1 ; Biol. Centr. 



Amer. Bot., II, 154; Ainer. Acad. Arts & Sci., XXXII, 19. 



Mexico, Andes of Peru, Bolivia, St. Thomas, W. I., and intro- 

 duced into W. Africa and Cape Verde Islands. Pedregal, Aug. 20 

 (157). 



98. Zexmenia aurea Benth & Hook, f. Gen., II, 371, in nota sub Wedelia; Biol. 



Centr. Amer. Bot., II, 172. 



Pedregal, Aug. 22 (191). 



99. Tagetes micrantha Cav. Ic, IV, 31, t. 352; DC. Prodr., V, 646; Biol. Centr. 



Amer. Bot., II, 222. 



Recorded by a number of botanists from Arizona and Texas 

 southward to Costa Rica. Pedregal, Aug. 22 (201). 



100. Pectis prostrata Cav. Ic., IV, 12, t. 324; DC, Prodr., V, 100; Biol. Centr. 



Amer. Bot., II, 226. 



Collected in Florida, New Mexico, Mexico, Colombia and the 

 AVest Indies (Cuba). " Romero macho " (Cuba) ; Pedregal, Aug. 

 22 (210). 



101. Stevia Eupatoria Willd. Sp. PL, III, 1,775; Bot. Mag., t. 1,849; Biol. Centr. 



Amer. Bot., II, 86. 



The specimens resemble Stevia linoides Schult. Bip., although the 

 inflorescence is flatter and more compact. The plant is, therefore, 

 doubtfully referred to the above named species ; North and South 

 Mexico. Pedregal, Aug. 22 (206). 



101b. Senecio praecox DC, Prodr., VI, 431. 



Senecio praecox is a composite plant inhabiting the volcanic beds 

 in the Valley of Mexico. It has a cylindrical stem rising three or 

 four feet from the ground with clustered, deeply lobed leaves at the 

 top. The plant stores up an abundant supply of water in the pith, 

 which is gradually used up during the dry season in Mexico, which 

 lasts from October to June. The flowers develop in April at the 

 expense of the reserved supply of water. Loss of water during the 

 dry season is prevented by the fall of the leaves, and by the protec- 

 tive cork and balsam secreted in the exo- and endocortex. The 

 water stored in the turgid discs of pith is gradually conducted by 

 the woody cells and tracheids, which penetrate into the medulla by 

 wedge shaped ingrowths, representing the primary bundles, to the 

 growing point where it is used. That this is the case, is shown by 

 the dry parchment-like pith membranes, which were left in a piece 

 of a stem which had remained in the dry state for over sixteen 



