1893.] Nucleus to Spore-formation in certain Liver-worts. 479 



plasmic portions of the four spores. The achromatic spindle is fairly 

 well marked, and runs up sharply to a point in each lobe, and a 

 structure can often be seen at the end which possibly represents the 

 presence of a centrosome. 



In Aneura pinguis the case is somewhat different. The lobing of 

 the spore mother cell is much more apparent than in A. multifida, 

 and just before division occurs, a portion of the dense protoplasm 

 which surrounds the nucleus (and which should probably be regarded 

 as an archoplasm) protrudes as an achromatic spindle simultaneously 

 into each of the four cell lobes. This takes place while the nucleus 

 is still resting, and thus a quadripolar spindle is formed. The nucleus 

 then becomes also lobed, in such a way that it assumes a tetrahedral 

 shape, with an angle in contact with each achromatic sheaf. I have 

 not, through scarcity of material, as yet been able to observe the 

 behaviour of the chromosomes in this species, but there is hardly 

 room for doubt that a simultaneous separation of the bodies into four 

 groups takes place. This conclusion is strongly supported by the 

 peculiar behaviour of the archoplasmic spindle already described. It 

 should be mentioned that the application of such stains as gentian- 

 violet and orange, or heematoxylin and orange, gives such clear results 

 that it is impossible to mistake the character of the process. 



The most conclusive results, as well as the most remarkable, were 

 obtained in the case of a tropical Liver-wort, Steetzia decipiens, which I 

 collected when in Ceylon two years ago. The division of the nucleus 

 takes place at an extremely late period in the development of the 

 spores. The intruding walls grow into the cavity of the mother cell 

 to such an extent as almost to touch the nucleus itself, whilst the 

 sculpturing so characteristic of the mature spore is quite obvious, 

 even before the nucleus exhibits any sign of approaching division. 

 I have been fortunate in securing a large number of preparations in 

 which all the steps are clearly shown, and have further succeeded in 

 getting the important stages photographed. The nucleus is invested 

 by a dense mass of protoplasm (archoplasm), and this, as in Aneura 

 pinguis, forms a quadripolar achromatic spindle whilst the nucleus 

 is still in the resting condition. The ends of the spindle severally 

 reach out to a point beyond the centre of each lobe. I have termed 

 the spindle achromatic, following the common usage, but, as a matter of 

 fact, it stains deeply with hsematoxylin, safranin, or gentian- violet a 

 point of some interest. The chromatic portion of the nucleus now 

 forms a large mass in the centre, and becomes four-lobed, the lobes 

 being united centrally till quite late. 



Then they become separate, and each breaks into two chromo- 

 somes of a rod-like shape, which are at first aggregated somewhat 

 irregularly in the centre, from which the achromatic spindles diverge. 

 Speedily, however, they arrange themselves in pairs, and each pair 



voti. LTV 2 L 



