Books and Current Literature. 295 



continuously for more than two decades, and give a reliable his- 

 tory of the appearance and movements of a number of species 

 which are now widely spread in the San Bernardino valley and 

 beyond. 



Zinger, in a paper recently published by the Imperial So- 

 ciety of St. Petersburg, gives an account of the four species of 

 Camelina found in Russia, viz. : 



(1) C. microcarpa, a wild plant of the steppes; 



(2) C. pilosa, which occurs as a weed in winter crops, and 

 is frequently found in southern Russia.; 



(3) C. glabrata, a cultivated plant occurring infrequently 

 in summer crops as a weed; 



(4) C. linicola, which occurs exclusively in crops of flax 

 and is especially characteristic in northern Russia. 



From biometrical studies and continued series of pure 

 cultures the author comes to the conclusion that changes taking 

 place in the order C. microcarpa, pilosa, glabrata, linicola consist 

 chiefly in a gradual transition from xerophytic to hydrophytic 

 types and increased size of the seed. The loss of xerophytic 

 characters consists in the gradual reduction of pubescence and 

 certain other changes in the external and internal structure of 

 the vegetative organs. 



The author believes that C. linicola (the species which grows 

 with flax) has arisen by a peculiar process of selection from the 

 cultivated C. glabrata, and that this latter had its origin in the 

 wild C. microcarpa. Cultures of C. glabrata with flax, or undi.-r 

 similar conditions, exhibit all the morphological and anatomical 

 characters of C. linicola. Nevertheless it is believed that the 

 latter species is no* the direct product of environmental forces, 

 but rather the result of a process of selection which takes place 

 in sorting and cleaning flax seed. Slight individual variations, 

 rather than mutations, according to this view, have afforded the 

 material for selection to act upon. 



Various American pines, particularly a number of 

 western species, have the habit of holding their cones unopened 

 for several or many years, and to this habit John Muir and others 

 have attributed the capacity of some of these species to hold their 



