392 TRANS. ST. LOUIS ACAD. SCIENCE. 



the following of the Prinus Group : ^. casianea with /? privoides, ^. Pri- 

 nus, and ^. bicolor.* 



^. Douglasti, Hook, is the only Californian oak which might be con- 

 founded with ^. Garryana ; but, if I understand it aright, it can always be 

 distinguished by its small oval, obtuse, bright brown, slightly hairy winter 

 buds; its smaller, more sinuate than lobed leaves, which, downy in early 

 youth, soon become glabrous on the upper side, with a bluish tinge, whence 

 it has received locally the name of Blue-oak, or Blue Mountain-oak. It 

 extends not as far north as Garryana, probably not into Oregon, but far- 

 ther south on the lower hills and mountains of the Pacific slope. 



^. undulata, Torr. Enough has been said in the introduction to this 

 paper and on p. 382 about the wide limits of variation which this species 

 enjoys; local botanists, however, are not agreed as to the relations these 

 forms bear to each other. We are safe in arranging all the varieties in two 

 groups; the first is characterized by larger, strongly lobed, darker green 

 and decidedly deciduous leaves, and narrower, ciliate calyx lobes; the 

 second has smaller, paFer, more rigid, mostly spinous-dentate, and — at 

 least southward — more or less persistent leaves, and broader, woolly calyx 

 lobes. In both groups the sweet and edible acorns are oval, oblong, or 

 sometimes elongated; the subhemispherical, sessile, short- or sometimes 

 long-peduncled cup varies from scaly to very knobby ; in the dark-leaved 

 forms the acorns are often thicker and shorter, in the pale group slender 

 and longer. Distinct as both groups seem to be, the original ^. undulata, 

 my var. yamesii, completely connects them. Var. Gavibelii, with broader 

 emarginate or even lobed divisions of the large leaf, on one side runs into 

 var. Gunnisoni with narrow and entire lobes, and on the other into var. 

 breviloba (.^. obtusiloba var. breviloba, Torr. Bot. Bound., and probably 

 ^. Durandii and ^. San Sabeana, Buckley) with sinuate or broad- and 

 short-lobed leaves. The forms of this group are found from Western Texas 

 through parts of Colorado, Utah, New Mexico, and Arizona, but not west 

 of the Colorado River. Var. Jamesii is a Gunnisoni with acute lobes of 

 the smaller, more rigid leaves, found thus far only from West Texas to 

 Colorado. The transition is almost imperceptible from this to the pale- 

 leaved forms which southward become evergreen, in so far as they lose 

 their old leaves not before the new ones develope. They do not extend as 

 far north nor east as the dark-leaved group, but farther southwestward 

 through the California desert and into the mountains bordering it on the 

 west. 



This pale-leaved group consists principally of var. pungens (.^. pungens, 

 Liebm. as to sp. Wright 664; var. IVrigktii, p. 3S2, which has con- 



* The insects iippear to understand the natural relations of the species of this group as 

 well as we do; on all of them, and on no other oaks, I have noticed a very peculiar gall — 

 for a gall I must take this excrescence to be — on the cups, singly or several together, usually 

 surrounded by fringe-like scales, sometimes hollow, sometimes cont;iining what looks like 

 a diminutive acorn. Entomologists are, I suppose, well acquainted with these galls. Some, 

 times they have been taken for minute abortive acorns from the axils of cup scales; but 

 cup scales are not leaf organs, and cannot well produce axillary buds. 



