BLAKESLEE, — SEXUAL REPRODUCTION IN THE MUCORINEAE. 205 



L. W. Riddle, Jamaica Plain, Mass. ; Prof. Geo. Klebs, Halle, Germany ; 

 Prof. C. S. Leavenworth, Shanghai, China ; Prof. G. R. Lyman, Han- 

 over, N. H. ; Prof. L. Matruchot, Paris, France ; Prof. A, C. Moore, 

 Columbia, S. C. ; Dr. E. W. Olive, Madison, Wis. ; Mr. J. B. Rorer, 

 Washington, D. C, and Nassau, Bahamas ; Prof. F. L. Stevens, Raleigh, 

 N. C; Mr. M. E. Stickney, Granville, Ohio; Prof. P. Vuillemin, 

 Nancy, France ; and the writer has himself obtained material from 

 Margarita and Caracas, Venezuela ; and Port au Prince, Haiti. 



Serial Cultures. 



In investig.ating the (+) and ( — ) strains of this species a number of 

 serial cultures were conducted to observe the effect of continued cultiva- 

 tion on the sexual activity. December 2, a sporangial series of both 

 strains from culture A was started in tubes of potato agar kept in a 

 culture drawer and the transfers continued up to the thirteenth generations. 

 A similar series was begun at the same time and carried on in the warm 

 oven at 26°-28°C. up to the twenty-seventh generations. From cultures 

 at the room temperature sporangial transfers could be made every third 

 or fourth day, while from those in the warm oven transfers could be made 

 a day earlier. In making transfers a mass of the mature sporangia was 

 generally used, though occasional pure transfers from single sporangia 

 were made in each series. In later tubes from 3 to 4 per cent of grape 

 sugar was added to the nutrient, and increased both ^the rapidity and 

 luxuriance of the growth. From tubes A(+)3 and A(— )3, the third 

 generations of A(+) and A(— ) strains, a mycelial series was started 

 December 1 1 . Each morning a piece of agar with the attached mycelium 

 was transferred with a platinum spatula into a new tube. In this way 

 the growth of the mycelium was uninterruptedly prolonged for over two 

 months and prevented from producing any sporangia whatever until 

 February 19, when the seventy-first tubes were reached and the series 

 discontinued. The last tubes of each of the three series were tested and 

 the growths in them were apparently unaffected in their sexual character 

 or activity, nor had one strain, as in the similar experiment with Mucor 

 Mucedo subsequently described, shown any tendency to lose its vitality. 



Morphology and Physiology of Conjugation. 



In a discussion of the morphology of zygospore formation in this 

 species it will not be out of place to quote from de Bary's ('66) paper ou 

 Rhizopus. According to his account zygospores form on low irregularly 



