ENGELMANN NOTES ON THE GENUS YUCCA. 3 1 



p. 485), confirm and adopt these differences. In S. Watson's 

 Botany of the 40th Parallel (Utah and Nevada), 1871, I have 

 briefly characterized the four sections of Yucca, as I now under- 

 stand them. 



The fruit in some Yuccas is pendulous, pulpy and indehiscent, 

 with a sort of crown or disc at base, consisting of the enlarged 

 remnants of the perigonal segments and the stamens {^Sarcoyuc-^ 

 ca) ; in another, thus far only imperfectly known, species the 

 originally fleshy fruit eventually dries up, and constitutes a spongy 

 pericarp, which never opens, and is apparently erect, with a disc 

 at base like the former ( Clistoyucca) ; in a third group, the erect 

 fruit is dry and capsular , the base is contracted into a short 

 obconical stipe ; it opens with three valves corresponding with the 

 carpels and dividing the primary dissepiments, the valves finally 

 divide again at tip ( Chcenoyucca) ; in the fourth group, repre- 

 sented like the second, by a single species, the pod is similar to- 

 that of the last section, but opens at tip through the middle of the 

 carpels loculicidally, the three valves remaining entire (^Hespero^ 

 yucca). 



The secondary dissepiments are usually incomplete at base 

 and top, and, at least in one form ( T. Jilainentosd)^ they are often 

 rudimentary throughout ; in Hesperoyucca they seem to tear 

 irregularly at the dehiscence of the capsules. 



All the Yucca fruits, but more especially the capsular ones, and 

 those of some species more than of others, are extremely variable 

 in shape, and this seems to be caused principally by the irregular 

 development of the seeds. When these fail near the middle, the 

 capsule becomes constricted (very often in the true T. Jilamento- 

 sa); when near the top, it usually is beaked (forms of T.rtipi- 

 cold); so that definite diagnostic characters cannot be derived 

 from these apparently so well-marked differences in the shape of 

 the capsule. In the species just named, and in the T. baccata, the 

 beak of the fruit may also be the result of the development of an 

 elongated style. 



The substance and the surface of the capsules would also seem 

 to afford good distinctions, for we find the capsule in some thin 

 membranaceous and smooth ; in others, thick, ligneous, cross- 

 wrinkled, with thick carinal and also lateral ridges, and some- 

 times warty ; but I have observed such differences in forms of the 

 same species, and especially in T. Jilamentosa^ which seems to 



