VOL. I.] 



Rhamnus Californica. 



243 



a foot in diameter. Wherever it grows in the open the leaves are 

 thick and rather small; but if grown in the shade they are much 

 larger and thinner, and this difference may often be observed in the 

 same plant if partly sheltered and partly exposed. The increase in 

 size as it grows in the shelter of the northern forests is to be ex- 

 pected, and is found also in CeajioiMis thyrsiflorvs and other shrubs. 



The w^ood has been too little examined; but in fresh cuttings an 

 inch or more in diameter, recently compared, the principal differ- 

 ence observed was in the much narrower annual rings of R. Cali- 

 fornica, showing its much less luxuriant growth. 

 ^ The claim of a real and constant difference in the venation of the 

 leaves will be found as fallacious in the case of Californica and 

 Purshiana as it is now known to be in the forms separated by Nut- 

 tall partly on this ground. Equally variable is the trivial character 

 of the channeled inidrib relied upon by Dr. Rusby. 



The fruit of our species of Rhamnus has been persistendy mis- 

 represented—even R. crocea was described by Nuttall as having 

 " fruit greenish or yellowish, usually i-seeded!" In all our species 

 of the Frangula section, the berries variously described as " black," 

 "blackish-purple," "dark-purple," are the same. They are all 

 globose when ripe; depressed-globose if 3-seeded, and as long or 

 longer than broad if i-2-seeded. R. Ca/?/bm/m is usually 2 -seeded, 

 but a very considerable proportion of the berries have three seeds, 

 and R. Purshiana varies in the same way. The drawmg of the 

 fruit of this species in Fl. Bor. Am. is very misleading--lookmg 

 more like Ceanothus than Rhamnus. R. rubra at the ongmal lo- 

 cality, the railway cutting above Truckee, is usually, though not by 

 any means invariably, 2-seeded; but one or two hundred yards 

 away, along the road to Lake Tahoe, older bushes are very com- 

 monly 3-seeded. It must be evident to everyone that so uncertam 

 a character is valueless in classification. The lobing of the fruit is 

 a similar persistent and annoying error. Prof. Coulter, for instance, 

 in writing of the three species occurring in Colorado, says: 



(c 



R. Caroliniana * * * fruit globose, 3-5eeded. 



R. Californica * * * fruit blackisn-purpie, wiui u.ui pu.^, . ^ 



R ^ Purshiana * * * fruit black, broadly obovoid, 3-lobed and 

 3-seeded." Now, every western botanist knows that the fruit of the 

 last two species is alike black and globose, without any lobing 



^j^ 



