DEPARTMENT OF BOTANICAL RESEARCH. 71 



temperatures, soil moisture, and other environie components, is depend- 

 ent upon the intensity or degree of the others together with an allow- 

 ance for rapidity of variation in these factors as well as time or duration 

 of exposure. It will be advantageous to realize some of the possibili- 

 ties made apparent by common observations. 



Among the more important environie reactions displayed by plants 

 used in these experiments were failure by depletion of storage organs, 

 vigorous vegetative activity resulting in supernumerary foliar and 

 floral organs, and disturbances of the reproductive cycle. 



Finally, the following general considerations were supported by the 

 results obtained: 



Species from cool regions may be more easily estabhshed in warm 

 places than the reverse, and montane plants may come to the sea- 

 shore more easily than the plants of maritime zones may spread 

 over a mountain. 



Dissemination movements are seen to be freer from regions pre- 

 senting clinmtic extremes to more equable climates, as is amply illus- 

 trated by the success of so inany species from the Atlantic States and 

 Arizona highlands on the Pacific seashore. Possibly the occurrence of 

 the succulent Opuntia in Saskatchewan may be considered as an ex- 

 ample of this as the predominant feature in dissemination. 



Not all groups of forms move and adapt themselves to new habitats 

 with the same facility. Thus the species characteristic of desert re- 

 gions represent an extreme development toward succulence and 

 xerophytism suitable for existence with a lessened water-supply, and 

 the retracement of the long way of morphogenic alteration by such spe- 

 cies is all but impossible. On the other hand, many mesophytic plants 

 show direct or indi^ddual alterations bj^ which they pass into arid areas 

 and maintain themselves for extended periods. 



The experiments again make it plain that the habitat in which a plant 

 may be found or in which it may have originated may not furnish the 

 most favorable environmental complex, as amply illustrated by the 

 behavior of species that have become weeds. In other words, the 

 fitness of a species for native habitat may not be so close as its fitness 

 for other as yet untried conditions. 



Hydrogen-Ion Concentration of Carmel Valley Soils, by B. M. Duggar. 



It has long been recognized that the reaction of the soil or, properly, 

 of the soil solution, is important in plant relations. Since 1909 a vast 

 airay of data has accumulated indicating the range of hydrogen-ion 

 concentration, or pH, within which micro-organisms grow most favor- 

 ably or enzymic changes occur with greatest velocity. With a degree 

 of accuracy the methods employed have been found applicable to the 

 soil solution, and the results of Gillespie, Plummer, Hoagland, and 

 others have yielded important exploratory data in respect to cultivated 



