562 4. Fortpflanzungslehre. 



to be absorbed, not thrown off. The nucleus contains a vacuolated karyosome 

 and masscs of chromatin. In the formation of spores two individuals encyst 

 together with their anterior ends in contact, After a time the chromatin 

 masses of the nucleus fragment and form chromidia within the nuclear mem- 

 brane, which meanwhile becomes thin. The karyosome throws out masses of 

 material which appears to be chromatin, and its remains then stain less deeply. 

 Near it a body begins to appear which takes nuclear stains readily, called by 

 the author the „achromatic mass". This gradually becomes elongated and 

 more distinct, and takes the form of a spindle, but at first neither chromo- 

 somes nor centrosomes are visible. As it develops streaks of chromatin gra- 

 nules appear on it, converging towards its poles. 



An aggregation of chromatin is thus formed at each pole, and as this 

 increases it becomes vesicular. During the aggregation of the chromatin gra- 

 nules at the poles of the spindle some of the spindle-threads are seen to run 

 into the midst of the karyosome-fragments, whence it is possible that the 

 chromatin granules are derived. No equatorial plate has been seen. The 

 deeply staining quality of the „achromatic mass" and the visible streaks of 

 chromatin near its poles suggest that the chromatin exists in the threads of 

 the mass in a finely divided state, and becomes concentrated into daughter- 

 nuclei at its poles. In the division of the daughter-nuclei two centrosomes 

 with astral radiations are clearly seen, but again no equatorial plate is 

 formed; the nucleus appears to be drawn out into a spindle. In its resting 

 stage a karyosome is present, but this disappears during division and its 

 origin in the daughter-nuclei is not clear. As the nuclei become smaller by 

 repeated division, the division figures become less complicated, and finally all 

 traces of spindle -formation disappear and the nuclei are reduced to small 

 masses of chromatin on the edge of the sporont, and by aggregation of the 

 protoplasm round them the gametes are formed. The gametes appear all 

 alike. Actual conjugation was not been, but the sporoblasts were observed to 

 develop into spores each containing eight sporozoites. 



Doncaster (Cambridge). 



1177) Lyle, Gr., Fecundity of Arctia caja L. 



(The Entomologist 43,568. p. 249. 1910.) 

 Ein abgeflogenes $ des Bären Arctia caja L. legte innerhalb 5 Tagen 

 1303 Eier. Nach seinem Tode wies der geöffnete Leib noch 150 auf. 



P. Schulze (Berlin). 



1178) Straslburger, E. (Bot. Inst, Bonn), Sexuelle und apogame Fort- 

 pflanzung bei den Urticaceen. 



(Jahrb. f. wissenschaftl. Bot. 47,3. p. 245—288. 4 Tafeln. 1910.) 

 Der erste Teil der Untersuchungen ist Urtica dioica gewidmet. Die Tat- 

 sache, daß weibliche Stöcke der Brennessel fruktfizierten, ohne daß männliche 

 sich in der Nähe befanden und daß alle so erhaltenen Früchte immer nur 

 weibliche Nachkommen lieferten, ließ die cytologische Untersuchung erwünscht 

 erscheinen, zumal da es Modilew ski, der die Notwendigkeit einer Befruchtung 

 bei Urtica dioica entschieden vertrat, nicht gelungen war, den Pollenschlauch 

 in den Samenanlagen nachzuweisen. 



Es zeigte sich, daß in der Tat eine Parthenogenesis hier nicht vorhanden 

 ist, obgleich isolierte weibliche Pflanzen unter Umständen Samen produzieren, 

 ohne daß man an ihnen das Vorhandensein pollenbildender Blüten feststellen 

 konnte. Diese Feststellung erwies sich allerdings als sehr schwierig, denn die 

 ziemlich häufig auf weiblichen Stöcken sich findenden hermaphroditen Blüten 

 zeigten meist wenige, oft sogar nur ein einziges Staubblatt. Der explosive 



