( 268 ) 



questions arise of which the answers may be of importance to cytology 

 itself. Especially hybrids with 0. gigas, which mutant probably 

 possesses twice as many chromosomes as Oen. Lam. itself, might 

 provide material for interesting cytological investigations. For this 

 purpose a knowledge of cytological development of the mutating 

 plant itself is, however, a first desideratum. 



The principal results obtained in this investigation, will now be 

 briefly stated. 



The floral development of Oenothera Lamarckiana was investigated 

 in 1895 by Pohl 1 ); this author arrived at conclusions, differing widely 

 from those obtained for other Onagraceae, for instance by Barciam r 8 ) 

 and by Payer ,1 ), for according to Pohl the development is not 

 acropetal, as found by the other investigators. It has now been found, 

 however, that Oen. Lam. like other Onagraceae has an acropetal 

 development of the tlower. In addition the chief points observed in 

 this development, are: 



1. The corollar stamen arises from the protuberance, which the 

 corolla forms on its inside. 



2. The ovary is the floral axis, which has become hollow. Only 

 the stigmas develop as 4 separate protuberances, alternating with 

 the calyx stamens. 



3. The ovary becomes quadrilocular by the growing inwards of 

 4 parietal septa, which stand before the calyx stamens and fuse in 

 the centre. 



4. The axis does not grow further: there is no columella. 



5. The placentae are differentiated from the edges of the septa. 



6. A corollar stamen and its petal have no common vascular 

 bundle. 



7. The ovule arises from periblem and dermatogen, except for the 

 vascular bundle in the raphe. 



The cytological development was studied both in the ovules and 

 in the stamens. A summary of the principal phenomena observed, is 

 here appended. 



When the mother-cells go into synapsis, the nuclear network contracts, 

 and a thin thread arises, in which chromatin particles can be seen. 

 This thread contracts to a tangle and continually becomes shorter and 

 therefore thicker; this is (dearly visible when the tangle unrolls itself 



') Ueber Variationsweite der Oenothera Lamarckiana von J. Pohl Oosterr. 

 botan. Zeitschrift Jahrgang 1895 Nr. 5 u 6. 



~) Untersuchungen ueber die Bluethenentwicklung der Onagraceae, Inaug. diss, 

 von D. P. Barcianu, Naumburg 1874. 



2 ) J. B. Payer, Organogénie de la Fleur. 



