34 Harslibcrgcr — Water Storage and Conduction in 



branches aforementioned, which may arise from the sides, and 

 after forming an elbow-shaped joint, grow up parallel with the 

 main stem (Plate VIII, Fig. 3). In other cases, the branches 

 have been broken off, and tlieir rounded stumps are found 

 covered with the weathered balsam which exudes. The 

 smooth stem harbors a number of epiphytes, among which 

 may be mentioned several species of lillandsia. The growth 

 of the epiphytes on the stem gives a somewhat venerable 

 and hoary aspect to the plants covered by them. In their 

 epiphytic growth, the Tillandsias simply embrace the host by 

 their holdfast roots, and an inspection shows no corrosion 

 of the cork by a ferment action, such as would happen 

 if the epiphytic roots derived a supply of food from Senccio 

 prcscox. 



The base or collar of our plant is usually swollen or 

 rounded (Plate VII, Fig. i). The roots come off from the 

 lower surface of this rounded base, and are several in number. 



The plant is surmounted b}' a dense crown of green leaves 

 (Plate VII, Figs, i and 2), which appear after the commence- 

 ment of the rainy season in Mexico (June to October). The 

 leaves are developed from the apices of the branches only, are 

 deciduous on the long terete petioles, cordate, much acuminate, 

 sub-hastiite, five to seven-lobed (Plate VII, Fig. 2 ). The 

 lobes are very acuminate, spreading ; the lower ones deflexed. 

 The texture is between membranaceous and fleshy. 



Before the rainy season begins, when the leaves appear, in 

 the months of March or April, or during the dr^- season, the 

 corymbs of yellow composite flowers occupy the apex of 

 the branch and bear several elongated, partially bracteolated, 

 yellow branches, thickened below the capitulum.* 



The structure of the stem is, however, vv'hat interests us 

 most in this plant. It is succulent, easily cut across, and pre- 

 sents in the living specimens, a very watery, firm internal 

 pith, a small cylinder of wood, a wide cortex with ch.lorophyll, 



* Curtis. — "Botanical Magazine," 3d sen, vol. X. t. 4803. 1854. 



