V. PLANT^i: WRIGHTIANJE. 33 



Humboldtiana, H. B. K. Nov. Gen. 8f Sp. 7. p. 40. t. 618. R. biniflorus, DC. Prodr. 

 2. p. 26 ] R. umbellatus, Cav. I — Rocky hills, Turkey Creek, June ; in flower. 

 Also near Monterey, Berlaiidier, Gregg. North of Queretaro, Gregg (in fruit). 

 Sonora Alta, Real del Monte, and Zimapan, Coulter (No. 1 - 3), and California, No. 

 113, Coulter. New Mexico, Wislizenus. — All the collectors agree in stating that 

 this is a shrub, from 2 to 3, or sometimes, according to Gregg, from 4 to 12 feet in 

 height. There is probably an error, therefore, in Kunth's statement that Hum- 

 boldt's specimens were from an " arbor procerrima." For our plant seems to be the 

 Rhamnus Humboldtiana, as well from Schlechtendal's account of original speci- 

 mens, as from Kunth's character and figure, except that the latter, but not the de- 

 scription, represents the upper leaves as acute. The species varies much in the size 

 of the leaves, &c., and in the number of flowers in the axillary clusters, just as do 

 most Rhamni. Wright's and most of our specimens have them raised on a short 

 common peduncle, as in K. Humboldtiana. I cannot think that K. glandulosa is 

 distinct, nor is the name a good one. The leaves are only pellucid-punctate. The 

 2 - 3-celled ovary has two ovules in each cell. The mature drupe is ovoid, 4 or 5 

 lines long, ripening from one to three seeds. Rhamnus biniflorus. Hook. Sf Am., 

 is another species of this genus. 



90. CoLDBRiNA Texensis, Grai/, PI. Lindh. 2. p. 169. Rhamnus'? Texensis, 

 Torr. 8f Gray, FI. 1. p. 263. On the Leona, June; in fruit. Common throughout 

 Western Texas. — This is a low, divaricately much-branched and spreading, flexu- 

 ose shrub, from 2 to 4 feet high, flowering from March to May. In Lindheimer's 

 collection of 1850 are fine specimens of what I take for a larger-leaved variety of 

 C. Texensis, but which Dr. Engelmann, under the name of Coluhrina stricta, con- 

 siders as specifically distinct. It is " erect, very little branched, only leafy at the 

 end of the slender branchlets, from 5 to 10 feet high ; the leaves pendulous (much 

 as in a Cerasus), larger, and it flowers much later (June 15), than C. Texensis; the 

 flowers and fruit are much the same." Engelm. The leaves on vigorous sterile 

 branches are often fully 2 inches long, oval or ovate-oblong, with a rounded base, 

 softly silky-tomentose underneath. These larger leaves on sterile branches are com- 

 mon to our Zizyphus, to Condalia obovata, and other Rhamnacese, as Dr. Engel- 

 mann remarks. 



MICRORHAMNUS, Nov. Gen. 



Calyx coloratus, 5-fidus ; tubo expanse subplano ; lobis patentissimis, ovatis, tri- 

 nervatis, nervo medio intus carinatis. Discus carnosus, pateriformis, calycis tubo 

 adnatus, margine subundulatus, ovarium superum cingens. Petala 5, obcordata, 

 unguiculata, calyce breviora. Stamina 5, petalis sequalia, iisdem libei-a : antherse 

 didymse, biloculares, bivalves. Ovarium liberum, ovoideum, biloculare, in stylum 

 columnarem angustatum : stigma emarginatum. Ovula solitaria. Fructus subdru- 

 paceus, siccus, ovoideus, osseus, calycis cupula parva suftultus, abortu subunilocula- 

 ris monospermus. Cotyledones foliacese, oblongse, planse. — Fruticulus ericoideus, 

 ramosissimus, glaber; ramis rigidis spinescentibus ; foliis alternis et in axillis vel 

 in ramulos brevissimos fasciculatis, persistentibus, parvis, linearibus vel spathulato- 



