Peklo's Work With Mycorhiza. 19 



several species of Penicillium were obtained, a form of Citro- 

 myces occurring most frequently. Pure cultures of these fungi 

 grew well in Raulin's fluid (in which tannin replaces sugar as the 

 source of carbon) ; and this is taken to confirm Peklo's theory that 

 the fungus in these mycorhizas is one adapted to utilizing the 

 tannins produced in the roots in response to the irritation of 

 the fungus. Inoculations of seedlings with the pure cultures re- 

 sulted in well-developed mycorhizas on beech roots, from 

 C%tromyces as well as from Penicillium. 



From the alder swellings he separated a species of Strepto- 

 thrix, and from Myrica a form of Actinomyces. Both organisms 

 grew well on a mixture of malt worts with potassium carbonate 

 and di-potassium phosphate. The Actinomyces showed certain 

 physiological similarities to pathogenic forms, and also to the 

 bacillus of tuberculosis. Two seedlings of alder were infected 

 with the pure culture of the isolated organism; the root-hairs 

 were entered by the fungus, without being injured, though they 

 showed the swelling and branching as described by Hiltner; 

 but no tubercles weie foimed on any of the rootlets. 



The dependence of the fungus upon the roots is inferred from 

 thi fact that the cultures (of Penicillium) thrive in solutions in 

 which tannin is the sole source of carbon, together with the con- 

 clusions of Reinitzer and Nikitinsky to the effect that these 

 fungi can not get their carbon from the humus, from which they 

 get only their nitrogenous mateiial. Tannin is produced in the 

 roots attacked by the fungi; thir (and perhaps also the character 

 of the cell walls) confines the fungus to the intercellular spaces. 

 Peklo offers no hypothesis as to the compensation which the 

 "host" receives from the fungus. 



THE CHEMICAL ORGANIZATION OF A TYPICAL FRUIT. 



By a. E. Vinson. 

 The cane sugar in a green date of the invert sugar type re- 

 mains as cane sugar for many weeks in spite of the presence of 

 large amounts of invertase. When, however, the physical in- 

 tegrity of the fruit is disturbed, as by grinding or crushing, in- 

 version of this sugar takes place with great rapidity. Pre- 



