366 BULLETIN OF THE 



by Flemming to take place in the nuclear substance ; for these oscilla- 

 tions occur at a time when the monocentric may be supposed to be giv- 

 ing way to the dicentric attraction. 



•y. Plants. — A part of the spindle metamorphosis of the nucleus, — 

 namely, the equatorial plate, — appears to have been seen at an earlier 

 date in the division of vegetable cells * than in that of animal cells. The 

 real significance of the disk was overlooked, however, in the belief that its 

 components were artificial products, — alterations produced in the albu- 

 minous fluid of the middle of the cell by the protracted action of water. 



Russow ('72) was the first to correct this mistake, and to establish, in 

 the year succeeding the appearance of Kowalevsky's paper, and quite in- 

 dependently of his discovery, the normal existence of granular zones in 

 certain plant cells similar to those seen by Kowalevsky. These were the 

 parent cells of spore and pollen elements. The observations in the case 

 of ferns were made only after a study of the less obscure structure in 

 Ophioglossum and Equisetum. It was in these that the nuclear plate 

 (Kernplatte Strasburger) was for the first time accurately observed, but 

 the less conspicuous spindle fibres were not seen. The relation of the 

 plate to the nucleus was, however, very cogently argued. The separated 

 halves of this nuclear disk were also seen, but not fully understood, nor 

 their mutual recession suspected. It was pointed out that the nuclear 

 plate, and the structure afterwards called by Strasburger cell plate, were 

 not identical, so that what is said (loc. cit., p. 51) concerning the " Korner- 

 platte " (cell plate) in the formation of spores in Marsilia is in no sense 

 to be referred to the nuclear structure mentioned. 



Russow's statements (pp. 89, 90) are as follows : " Neben Mutterzellen 

 von dem geschilderten Aussehen [i. e. with a very large, finely granular, 

 spherical nucleus, usually eccentric in position], findet man (bei Polypod. 

 vulgare und Aspid. Filix mas) andere, die statt des Kerns eine kreis- 

 formige Platte von J bis § Durchmesser der Mutterzelle fiihren, deren 

 Flache grob granulirt, deren Rand, wenn man auf denselben nach Dreh- 

 ung der Platte um 90° herab sieht, wie aus langlichen Kornchen, oder 

 kurzen Stabchen, die hell und stark lichtbrechend sind, zusammengesetzt 

 erscheint. Grosser und scharfer ausgepragt sind diese Kornchen- oder 

 Stabchenplatten in den Sporenmutterzellen der Ophioglosseen und Equi- 

 setaceen (Figs. 121, 122, 123, 126); am grossesten und in ihrem Bau 

 am deutlichsten erkennbar fand ich die Flatten in den Pollenmutterzellen 



* Hofmeister, Die Lehre von der Pflanzenzelle (1867, p. 82, Figs. cZ and e). See 

 also the explanation of the figures. 



I 



