172 Botanisches Centralblatt. — Beiheft 3. 



a Single trunk. The crown of Quercus fFig. 4) is larger, oftener 

 and more finely branched than Platanus. Further, the leaves of 

 Platanus are large, five lobed, ratlier thick, leathery, dark greeu 

 and deciduous. The wool whieh covers the leaves when they 

 unfold persists for a long time. The leaves of Quercus are more 

 abundaut, thin, hard, dark, evergreen, small and except for the 

 small marginal spines entire. The wool of the young leaves soon 

 disappears so that they soon become smooth, and on the upper 

 surface even glistening. 



In the regions not oecupied by trees we find numerous shrubs 

 and herbs. The shrubs of the caSon formation are usually taller 

 than those of mountains and foothills and are more regularly 

 branched. The tendency is much more toward a mesophytie than 

 a xerophytic type. The branches are usually straight. The leaves 

 are of medium size and varying shape. They are seldom entire 

 and often Compound. 



The characteristic forms are Eriodyction tomentosum Benth., 

 Romneya Coulteri Harv., Ämorpha californica Nutt., Trichostema 

 lanatum Benth., Rosa californica Schlecht., Alimulus glutinosus 

 Wend., Photinia arhutifolia Lindl., Zauschneria californica Presl, 

 Pentstemon cordifolius Benth,, Eriodyction^ Trichostema and Mimulus 

 have and abundant covering of farge gland hairs on all of their 

 parte. 



Climbing forms are represented by Yitis Californica Benth. 

 and Rhus Toxicodendron L. 



In Canons which no longer have running water, Opuntia is 

 not uncommon, 0, Engelmanni SaJm is the common form. It usually 

 takes on the spreading rather than the erect habit and its joints 

 are not more than half the size of the hill forms. 



The herbaceous flora of the cailons is a large one but its 

 composition does not vary as often or as regularly as that of the 

 foothills. Many forms are typically mesophytie in nature. The 

 more characteristic forms include: Paeonia Brownii Dougl. {cali- 

 fornica Nutt.), Thalictrum polycarpum Wats., Claytonia perfoliata 

 Donn., Geranium carolinianum L., Platystemon denticulatus Greene, 

 ßloovieria aurea Kell., Galium Aparine L., Verhena prostrata R. Br., 

 Phacelia Whitlavia Gray, Mimulus luteus L. var. depauperatus 

 Gray, Mentha cavadensis L., Pycnanthemum californicum Torr., 

 Solidago occidentalis Nutt. and Houttynia californica B. et H. 



In the damper parts Equisetum arvensis L., E. hiemale L. 

 and E. Telmateja Eiirb. are often to be found. Only one fern 

 grows on the canon lioor, Pteris aquilina Kuhn. It is much snialler 

 than when growing in raoist open sandy Situation». Sclerenchyma 

 is very strougly developed, particularly in the rhizome. 



River Bed Formation: During the wet season shrubs 

 about 2.5 meters high constitute nearly the enlire Vegetation of 

 this formation. In manner of growth these forms resemble the 

 cafion shrub. The leaves are however always entire and usually 

 smooth. The major porüon of this shrub growth is made up of 



