ENGELMANN — NOTES ON AGAVE. 293 



ovary in common with the true bulbiferous Amaryllidaceae, 

 distinguished by a naked scape and an involucral spathe. The 

 numerous horizontally-flattened black seeds, mentioned already 

 by Salisbury as being common to Yucca and Agave, are not 

 found in the true Amaryllis family ; nor do these possess the fili- 

 form embr\'o which diagonally traverses the whole length of the 

 albumen. Other interesting diflerences are found in the valvate 

 aestivation of the Agaveae and in their commissural* stigmas. 



TRUNK. 



The majority of the Agaves are acaulescent and monocarpic ; 

 the short subterranean trunk continues to grow for yearst until 

 vigorous enough to evolve the flowering stem, a continuation of its 

 axis, and dies after bearing fruit. During its growth a wreath of 

 numerous thick, fleslw, white root-fibres is developed every spring 

 from its lower part, while the lowest, oldest part of the trunk dies 

 and rots away. This is the case at least in Ag'ave Virginica. 

 A few Agaves have persistent trunks, sometimes of considerable 

 dimensions ; these produce flowers repeatedly, just as the caules- 

 cent Yuccas do, from axillary branches, after the terminal bud of 

 the main axis has fulfilled its destiny and died. These secondary 

 branches are initiated by a pair of short and clumsy, strongly 

 carinate leaves, which may be considered as representing bud- 

 scales {^Niederblaetter)^ as I noticed in vigorous specimens of 

 A. Boiickeaiia. y^cohi^ and A. chlorocantha., Salm, in the Berlin 

 botanic garden, 1869. 



In the acaulescent Agaves the subterranean trunk dies entirely, 

 or for the greater part; but in A. Americana^ and probably in 

 the majority of the species, it first emits from the axils of decay- 

 ing leaves numerous offshoots, which grow into separate young 

 plants and thus propagate the individual. In A. Virginica it pro- 

 duces sessile lateral buds, which grow up, still adhering to the 

 persistent part of the old trunk, a sort of corm, giving to the plant 



* StigTnas formed by the commissures of the carpels, therefore alternating with these, a 

 comparatively rare case. The common form is the carinal stigma, formed by the tip of the 

 carpel itself or its carina, therefore opposed or rather superimposed to the carpel, while the 

 true Amaryllidaceae have an imbricate aestivation and carinal stigmas, and so have Yucca 

 and i>erhaps all Liliaceae. 



t In A. Americana, in its home, eight to fifteen or more years ; under more unfavorable 

 circumstances, in cultivation in colder countries, much longer, eren, it is said, fifty or a hun- 

 dred years, whence the name century-plant. 



