296 BOTANICAL GAZETTE [april 



plant tissues retain chiefly the basic ions of the salts dissolved 

 in the cell contents of the plant tissues before they began to decay, 

 thus freeing the acid ions. Skene (24) has found that various 

 species of Sphagnum thrive best in acid solution because mineral 

 solutions, although usually physiologically harmless, may be 

 ecologically harmful. 



Work by Livingston (14), Dachnowski (6, 7), the writer (19), 

 and others (20), indicates that the inhibition from sphagnum bogs 

 of plants other than bog xerophytes is not due to acidity, or to 

 low surface tension, or to high osmotic pressure of the soil solu- 

 tion, but is due in part to the presence of toxic substance or 

 substances, in the soil solution. 



Many workers (8, 9, 15-18, 25-27) have found that cultivated 

 crops and plants grown in cultures have a favorable or an unfavor- 

 able influence on other plants growing in the same substratum 

 either at the same time or subsequently. Food supply and toxins 

 have been suggested as means through which this influence may 

 be exerted. Czapek (5) finds that the roots of plants are 

 injured when the surface tension of the bathing solution is lower 

 than 0.66. 



Sherff (23) found in Skokie marsh near Chicago that where the 

 rhizomes of Sagittaria latij'olia had penetrated the decaying rhizomes 

 of Nymphaca advena, they themselves had begun to decay. 



STERILE CULTURES OF SEED PLANTS 



More or less success has been attained by various workers in 

 attempts to grow seed plants under sterile conditions. Harrison 

 and Barlow (ii) tried sterilization by dry heat, moist heat, 

 sulphuric acid, calcium hydrate, formaldehyde, and mercuric 

 chloride, and abandoned all of these means. They succeeded in 

 getting sterile cultures of certain legumes by treating the unopened 

 pods with mercuric chloride, opening them with flamed forceps, 

 and transferring the seeds to a very small quantity of boiling water 

 in sterile test tubes. 



Wilson and Harding (30) tried alcohol, formaldehyde, and 

 mercuric chloride as a means of sterilizing alfalfa seeds, but found 

 that when the seeds were sterile, the germination was very low. 



