TREES AND SHRUBS 119 



THE BUCKTHORN FAMILY (Rhamnaceae) con- 

 tains 4 genera of shrubs, all of winch are of more or less im- 

 portance for decorative purposes. Two of them (Zizyphns 

 lycioides and Condalia spathulata)ave. inhabitants of the most 

 barren of the mesas in the southern part of the State. They 

 are each spiny branching shrubs 4 to 6 feet high, sometimes 

 assuming the form of a stunted tree with widely branching 

 top. The leaves are small and simple ; the flowers are in- 

 conspicuous; the fruits are small black berries. These plants 

 will prove of value for cultivation in situations where the 

 water supply is very meager and the soil poor and rocky. They 

 may be difficult to transplant, but once established in even 

 the driest situations, they will probably persist. 



Three species of Buck Thorn (Rhamnus spp.j occur in 

 the higher timbered mountains of this State. They are un- 

 armed- shrubs 3 feet high or more, with rather large alternate 

 leaves and inconspicuous small flowers, followed by small 2 

 to 4-seeded rather dry berries. For massing they would be 

 useful at levels above 7,000 feet. 



Three species of the genus Ceanothus occur in the moun- 

 tains between 5,000 and 8,000 feet. One of these, Ceanothus 

 greggii, produces numerous small white flowers on its stiff 

 woody stems, and is a low shrub 3 to 4 feet high, which might 

 be used in plantations of other arid land plants. The other 

 two species are smaller and more leafy shrubs of the higher 

 levels. 



RHAMNACEAE. Buckthorn Family. 

 More or les> spiny shrubs 6 feet high or | esSi witn s j mp ] e 

 leaves having- small stipules; flo.wers perfect or polygamo-dioeeeious, 

 mostly small and inconspicuous; calyx 4 or 5 sepals, valvate, with a 

 disk lining the hypanthium : petals 4 or 5 or wanting; stamens 4 or 

 5, opposite the petals on the throat of the hypanthium or the disk; 



