Atkins — Factors affecting Hydrogen ton Concentration of Soil. 407 



It was found that when transplanted the plants always died in the case 

 of Anagallis tenella, Ccdluna vulgaris, Vrosera rotundifolia , Erica cinerea, 

 Marthecium ossifragum, Scilla autumnalis, Sedum anglicum, and Vaccinium 

 Myrtillus. Elsewhere E. cinerea and E. vagcms grew well in a garden at 

 pH 6-2. 



Among those which flourished were Antliyllis vidneraria, Armeria ndgaris, 

 and Sedum acre. Eeference to Table II shows that the pH value of the soil 

 is correct for the latter, but incorrect for the former list. 



Sedum album also flourished, but has not been found growing wild. This 

 is sometimes called S. anglicum by florists, which serves to explain a puzzling 

 instance in which S. anglicum was alleged to grow well in limestone gardens 

 near Plymouth and Cork. The two were evidently confused, as the species 

 of this genus often are (Praeger, 1921). It is stated in the Cybele 

 Hibernica that S. album grows wild in several places near Cork. Due 

 attention to the correct soil reaction will render the growth of wild flowers 

 less precarious in captivity. Wherry (1918) has pointed out that, though most 

 orchids require an acid soil, yet certain species, of Cypripedium for example, 

 have slightly alkaline habitats. 



The hydrogen ion concentration of natural waters in relation to plant ^ 



distribution. 



"When considering the reaction of the soil it is natural to inquire into 

 that of the water draining or springing from it, and the relation it bears to 

 plant distribution, Mention has already been made of the existence of 

 certain springs which contain sulphuric acid. These, however, are rather 

 rare. 



Birge and Juday (1911) made a detailed examination of the Wisconsin 

 lakes, correlating the animal and vegetable life with the alkalinity of the 

 water to phenol phthalein, or its acidity to the same indicator. This mono- 

 graph studies the oxygen content of the water also, and is a mine of informa- 

 tion. Chambers (1912), too, observed the seasonal changes in the alkalinity 

 and oxygen content of the ponds in the Missouri Botanic Gardens according 

 as the algae abstracted carbonic acid and evolved oxygen. The numerous 

 reseai'ches on the hydrogen ion concentration of sea water and its relation to 

 the photosynthetic activity of the algal plankton will be discussed elsewhere. 



More recently Saunders (1921) has shown that the water from wells and 

 of the town supply at Cambridge is very constantly at pH 7'l-7'2, the 

 districts examined being chalk and gault. Running streams, however, lose 

 carbon dioxide till the bicarbonate equilibrium with the gases of the air is 



