mVERTEBRATA, ORYPTOGAMIA, MICROSCOPY, ETC. 309 



Chrysomyxa Abietis, whicli may be regarded as an gecidio-form in which 

 the production of aecidia has been suppressed, and whose uredo-form 

 is also unknown. The genus Chri/somyxa may then be divided into 

 two subgenera, Euchri/somyxa ( = Melampsoropsis Schroeter), embracing 

 C. Ledi and Rhododendri, and Leptoclirysomyxa, embracing G. Abietis 

 only. As to the position of this genus, he would place it near to, 

 rather tlian include it under, the Coleosporie^. 



Finally, De Bary regards Chrysomyxa Abietis as in reality a very 

 simple tremellinous fungus, or at all events as presenting a link 

 between the Uredineas and the Tremellini, and confirming the close 

 relationshij) of these families already suggested by Tulasne. 



Excrescences on the Roots of the Alder.* — M. Gravis returns to 

 this subject ; and while thinking that farther investigation is yet 

 required to clear up all the difficult points connected with it, is of 

 opinion that the fungus frequently found in the cells is an accidental 

 accompaniment rather than the cause of the disease. He finds that 

 some of the cells in the part affected contain an amorphous viscid 

 mass resembling more or less the plasmodium of the Plasmodiopliora 

 Brassicce found by M. Woronin in the excrescences on the roots of the 

 cabbage, while neighbouring cells contain granules which may be the 

 spores of the same organism. In other cells again are ovoid masses 

 which may be the Schinzia Alni of the same author,| but no distinct 

 hyphie nor spores were to be detected. The only means of setting 

 the question of the cause of the disease at rest would be to induce the 

 spores to germinate artificially ; but all attempts at this have hitherto 

 failed. 



Influence of Temperature on the increase of Yeast.J— The efiect 

 of various temperatures on the rate of increase of yeast-cells has been 

 made a subject of study by R. Pedersen, the test employed being 

 counting the number of the cells. 



Carefully planting out 100 yeast-cells, it was found that during a 

 space of twenty-four hours they increased to 225 at 4° C, to 476 at 

 13° -5, to 120G at 23°, to 1759 at 28°, to 039 at 34^ while at 38° no 

 increase had taken place. The " optimum " temperature is therefore 

 between 28 ' and 34^ C, and nearer to the former ; on each side of the 

 optimum the rapidity of increase diminishes, and at 38° C. it ceases 

 altogether. During the second day the uuiltiplication of the yeast- 

 cells was much more rapid at 15°* 5 than at 4° or at 23' ; at the latter 

 temperature it had almost entirely ceased. After eight days the 

 nutrient fiuid sowed with an ctpial number of yeast-cells contained 

 nearly the same number of cells, but twenty times that originally 

 introduced, whether the temperature were 13 '5 or 23^ 



Tli(! total result of the experiments was that temperatui'e exorcises 

 a great influence on the rapidity with whicli yeast-cells jjropagate, 

 but that it produces no alteration on the total number of cells finally 



* ' Bull. Soc. Roy. Bot. Belgique,' xviii. 2n(l Div. (1879) p. 52, and xix. 2nd 

 Div. (1S80) p. l.'S. 



t Sco tlii.s .lournal, ii. (1879) p. 1)29. 



i 'Meddeldtr Ira Cnrlabcrg liulKnutniiit,' II, it I. p. 38; gco ' Naturforscher,* 

 xii. (1879) p. 444. 



