96 Fungi, Bacteria und Pathologie. 



This paper deals with the conditions influencing or asso- 

 ciated with the production of zygospores in the Mucorineae. 

 In a culture of Rhizopiis zygospores were found to appear 

 at the junction of certain mycehal coionies. By following this 

 Suggestion the author has found an explanation of zygosporic 

 activity quite different from any heretofore proposed. The 

 principal features of Dr. Blakeslee's summary are about as 

 follows: (1) The production of zygospores in the Mucorineae 

 is conditioned primarily by the inherent natura of the individual 

 species and only secondarily by externa! factors. (2) According 

 to their method of zygospore formation, the Mucorineae may 

 be divided into tv/o main groups, the homothallic and the 

 h eter thalli c. (3) In the homothallic group, zygospores are 

 developed from branches of the same myceiium and can be 

 obtained from the sowing of a Single spore. (4) In the hetero- 

 thallic group, zygospores are developed from mycelia diverse 

 in character and can never be obtained from the sowing of a 

 Single spore. Every heterothallic species is an aggregate of 

 two distinct strains, through the interaction of which zygospore 

 formation is brought about. (5) These sexual strains in an in- 

 dividual species show a difference in Vegetation luxuriance, and 

 the more and less luxuriant may be designated by the use of 

 (-}-) and ( — ) slgns respectively. (6) A process of imperfect 

 hybridization will occur between unlike strains of different he- 

 terothallic species. (7) The general conclusions are (a) that 

 the formation of zygospores is a sexual process; (b) that the 

 myceiium of a homothallic species is bisexual; (c) while the 

 myceiium of a heterothallic species is unisexual ; (d) and further, 

 that in the (-f-) and (— ) series of the heterothallic group are 

 represented the two sexes. 



Dr. Blakeslee iscontinuinghisresearches atthe Botanisches 

 Institut, Halle, Germany, and would be glad to correspond 

 with any one who would be willing to assist him in the collection 

 of material for work in the Mucorineae. 



Charles J. Chamberlain (Chicago). 



DüCOMET, V., La Brunissure des vegetaux et sa signi- 



lication physiologique. (Assoc. fran9aise pour l'avanc. 



des Sc, Angers, seance du 6 aoüt 1903. Public en nov. 1904. 



XXXII. p. 697—707.) 



La brunissure est un simple accident physiologique, car les pro- 

 ductions caracteristiques du mal et susceptibles d'isolement ne peuvent 

 se cultiver; les inoculations methodiquement conduites ne donnent aucun 

 resultat; tous les caracteres macro- et microscopiques de la maladie 

 peuvent etre realises experimentalement par des moyens physiques. 

 Donc le Plasmodiophora et le Pseudocommis Vitis doivent disparaitre en 

 tant qu'organismes vivants. 



Les alterations observees, qu'elles affectent le contenu cellulaire ou 

 des produits exsudes ä la iacon d'un miellat, sont le resultat d'une 

 exosmose de l'eau du cytoplasme et des leucites, assez lente pour per- 

 mettre ä ces deux Clements de la cellule de reagir et de modifier ä !a 



