294 Marquette, Manifestations of polarity in plant cells which usav. 



equal distances from each other. Nägeli 1 ) in 1844 confirmed tlie.se 

 observations. Botli Von Mohl and Xägeli show fibers in their figures 

 which represent spindle or connecting-fibers. neither of them, 

 howewer. reeognized their significance for nuclear or cell division. 

 Strasburger, 2 ) in 1880. forthe flrst time äescribed nuclear division 

 in the spore-mother- cells of Anthoceros and he ascertained that 

 the flrst karyokinetic figure is so oriented that each of the spindle- 

 poles lies niidway between two chromatophores, nuclear division 

 not coinmencing until the ehromatophore has divided twice in 

 succession and the four daughter chromatophores have taken their 

 Position about the nucleus. He does not directly describe the 

 position of the spindles of the second division but judging from bis 

 Statements regarding the positions of the four tertiary nuclei it is 

 to be concluded that the poles of the second spindles are directed 

 each upon one of the four chromatophores. As far as the chroma- 

 tophores themselves are concerned Strasburger's Observation confirni 

 the earlier accounts of Von Mohl and Nägeli. Strasburger also 

 describes the connecting fibers in the spore-mother-cells of Antho- 

 ceros as extending between the chloroplasts. not between the 

 nuclei. and points out that this is an exceptional occurrence. Davis 3 ) 

 in 1899 published a paper on the spore-mother-cells of Anthoceros 

 in which. however. he does not materially extend the observations 

 of the earlier workers as far as the chromatophores are concerned. 

 neither does he mention having observed any relation between 

 the position of the spindle and the position of the chromatophores. 

 Van Hook 4 ) also made some observations on cell division in Antho- 

 ceros He gives an interesting figure 5 ) of a cell-plate stage showing 

 numerous connecting fibers passing around the relatively small 

 nucleus on all sides and centered upon the chloroplasts. Van Hook 

 does not enter into a description of spindle formation and nuclear 

 division. 



The macrospore mother cells of various Isoetes species show 

 conditions which resemble those in the spore mother cells of 

 AntJwceros. Tscliistiakoff. 6 ) and Strasburger 7 ) were the 

 first to call attention to the structure of these cells and they were 

 later more fully investigated by Fitting. 8 j Fitting found a dark 

 mass consisting of starch grains and coarsely granulär plasm lying 

 against one siele of the still undivided nucleus of the macrospore- 



1 ) Xägeli. C. : Zellkerne. Zellbildung und Zelhvachstum bei den Pflanzen. 

 (Ztscbft. f. wiss. Bot. Bd. I. 1844. p 49.) 



z ) Strasburger. E: Zellbildung und Zellteilung. 3. Aufl. Jena 1880. 



3 ) Davis. B. M: The spore mother cell of Anthoceros. (Bot. Gaz. Vol. 

 XXYIII. 1899. p. 89.) 



i ) Vau Hook. J. M.: Notes on the division of the cell and nucleus in 

 liverworts. (Bot (iraz. Vol. XXX. 1900. p. 394.) 



5 ) 1. c. PI. XXLIl. Fig. 13. 



G ) Tschistiakoff. J.: Beiträge zur Phvsiologie der Pflanzenzelle. (Bot. 

 Ztg. Bd. 33. 1875. p. l.i 



-') 1. c. 



8 ) Pittiug. H.: Bau- und EntwickeluDgsgeschichte der Makrosporen von 

 Isoetes und Selaginella und ihre Bedeutung usw. (Bot. Ztg. Bd. 58. 1900. p. 107.) 



