Biologie. — Cytologie und Befruchtung. 339 



ß ESSEY, C. E., Weight of dandelion-down. (Science. N. S. 



XX. p. 119. July 22, 1904.) 



From observations by d'Allemand, it is estimated that more 

 than two and a quarter millions of dandelion-downs are required to 

 weigh a kilogram. Trelease. 



Allen, Chas. E., Chromosome Reduction in Lilium cana- 

 dense. (Bot. Gazette. Vol. XXXVII. 1904. p. 464—469.) 



In the pollen mother cells of Lilium canadense 

 the spirem is not completely formed before synapsis, 

 but before synapsis parallel threads are visible in many portions 

 of the nucleus. The double nature is not due to an early 

 jongitudinal split but to the presence of two distinct threads. 

 Early in synapsis the threads fuse, forming a Single thread. 

 After synapsis the spirem becomes evenly distributed throughout 

 the nuclear cavity and splits longitudinally. From its many 

 points of contact with the nuclear membrane the thread be- 

 comes drawn in so that the greater part of its mass is at the 

 center of the nucleus, giving rise to the second synapsis" as descri- 

 bed by Miss Sargant. Twelve loops are then formed as de- 

 scribed by Schaffner, but the peripheral region of the loop 

 is the region of Separation between two adjacent chromosomes. 

 Each chromosome consists of two portions, the products of 

 a longitudinal Splitting, which are twisted about each other. 

 The Separation in the heterotypic division is along the line of 

 longitudinal fission which the spirem underwent before its 

 segmentation. First before the complete Separation, each 

 chromosome splits longitudinally. The V shaped chromo- 

 somes of the second mitosis in the pollen mother-cell 

 are identical with the daughter chromosomes of the first 

 division. The origin of the Single spirem from the fusion of 

 two separate threads offers an explanation of the sudden appea- 

 rance of the reduced number of chromosomes. The spirem of 

 each nucleus is composed of substances derived in equal pro- 

 portions from each parent, but there is no fusion of hereditary 

 substances until the mother-cell stage is reached. 



A füll paper with figures will follow. 



Charles J. Chamberlain (Chicago). 



JANSSENS, F. A. et Ad. Mertens, Etüde microchimique et 

 cytologique d'une Tovula rose. (La Cellule. T. XX. 

 1903. p. 352—368. Mit 2 Tafeln.) 



Aus einem englischen Biere wurde eine Rosahefe isolirt 

 und deren Eigenschaften näher studirt. Ausser einem eigen- 

 thümlichen Verhalten des Kernes, wurde besonders constatirt, 

 dass die Farbe von Carotin oder einem Carotin- ähnlichen 

 Körper herrührt, und dass dieselbe vom Lichte in soweit be- 

 einflusst wird, als Dunkelkulturen eine intensivere Farbe be- 

 sitzen wie Culturen, welche dem Lichte ausgesetzt sind; auch 

 die Form der Zellen ist dabei verschieden. Hauptsächlich 



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