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11903] PRIMARY NUCLEUS IN SYNCHYTRIUM 407 



Rosen ('93) touched lightly upon Sy nchytrium Taraxaci, and 

 his results a^g^ree with those of Daneeard to the extent that he 



^,^v. ,,*^iv Cl.WO^ V^X J_^O.i.t^ 





describes a direct division in the primary nucleus. This divi- 

 sion however is so different in type from that described 

 Dangeard that it certainly could not have been described or 

 figured from the same structures. In the primary nucleus Rosen 

 finds that the chromatin loops into a spirem, the nucleolus 

 divides, the halves migrating to the forming daughter nucleus. 

 The nucleus then constricts in the middle, thus completing a 

 division of the nucleus in its spirem condition without the aid of 

 the usual achromatic structures. He asserts that as successive 

 divisions follow they assume more and more the character of 

 mitosis, eventually presenting a typically mitotic division. 



While discrepancies exist between these two authors regard- 

 ing the details of the amitosis, they agree that mitosis is the 

 exception and amitosis the rule; also that the primary division, 

 2. €,, the first division of the one primitive nucleus of each sorus, 

 \^ a direct division. 



The present investigations have been exclusively concerned 

 with S. decipiejis Farl., and our results are directly comparable 

 therefore with those of Dangeard and Rosen only in so far as 

 different species of one genus may be expected to agree in cyto- 

 logical detail. However, the work on Fucus (Oltmanns. '89) 

 and Albugo (Stevens, '99, '01) shows more specific cytological 

 variation than a priori yi^^vn^nX, would admit. 



The caption of the present article, indicating that the primary 

 division \s mitotic, emphasizes on^ of the chief features of 

 divergence between these results and those of Dangeard and 

 Rosen. We may here indicate also that in afifirming that the 

 primary division may be mitotic we in no way set aside the pos- 

 sibility of its being sometimes, even frequently, amitotic. There 

 are many peculiar structures to be found in the sori of Synchy- 

 trium, which it seems impossible to reconcile with universal 

 mitotic division. A consideration of these leads to conclusions 

 at variance again with those of Dangeard and Rosen regarding 

 the details of the amitotic division. Discussion of these struc- 

 tures Is reserved for a separate paper, the present one being lim- 





