Cytologie und Befruchtung. 35 



•distribution of somatic chromosomes is effected. The original 

 Iongitudinal fission frequently bccomes apparent in the iate 

 prophase and later stages of this division, and it is this that 

 provides for the fission occuring in the next (homotype) 

 mitosis. Thus the Heterotype is seen to be an intercalated division 

 that has the effect of halving, by distribution, the number of 

 chromosomes whilst the homotype is the completion of the 

 mitosis that was delayed owing to the supervening of the 

 heterotype. J. B. Farmer. 



Holden, R. J., and Harper, R. A., Nuclear divisions and 

 nuclear fusion in Coleosporium sonchi-arvensis Lev. 

 (Trans. Wisconsin Acad. of Sciences, Arts and Letters. Vol. 

 XIV. 1903. p. 63—82. Plates I and II.) 



At certain stages in the life history of this rust, the cells 

 contain two nuclei and at other stages but one nucleus. The 

 uredospore, and the cells of the mycelium to which it gives 

 rise, contain two nuclei which divide by conjugate division, i. e., 

 each nucleus contributes to the two daughter cells. The 

 teleutospore produced from this mycelium is the last binucleated 

 cell of the series. The two nuclei of the teleutospore fuse, 

 alter which the teleutospore at once germinates into a four 

 celled promycelium, each cell of which, contains but a Single 

 nucleus. Each of the four cells of the promycelium produces 

 a uninucleated sporidium. The first division of the nucleus of 

 the sporidium is not followed by cell division, but starting with 

 the sporidium there is developed a mycelium of binucleated 

 cells. In short. from teleutospore to sporidium the cells are 

 uninucleated. while from sporidium to teleutospore they are 

 binucleated. 



The two nuclei which fuse in the teleutospore have main- 

 tained a separate existence throughout almost the entire life 

 cycle of the rust, and there is some evidence that the chromo- 

 somes in the division of the fusion nucleus are collected into 

 two groups, representing, possibly, the chromosomes of male 

 and female nuclei. While there is no proper cell fusion, the 

 union of nuclei more or less separated in origin is not out of 

 harmony with our conceptions of sexual reproduction in other 

 groups of plants. Charles J. Chamberlain (Chicago). 



JUEU Ueber den Pollenschlauch von Cupressus. (Flora 

 Bd. 93. 1904. p. 5b— 62 und Taf. III.) 



Bei den bis jetzt genauer untersuchten Cupressineen (Biota, 

 Juniperus, Thuja) entwickeln sich im Pollenschlauch zwei Sperma- 

 zellen, die beide im Stande sind, ein Archegon zu befruchten. 

 Taxus und wahrscheinlich auch Podocarpus lassen die eine der 

 zwei früh verkümmern; bei den Abietineen finden wir schliesslich 

 auch nur eine Spermazelle normal. 



3* 



