304 Be e r , Development of tlie polleu grain and antlier of some Onagraceae. 



Tlii-s continuous nuclear inultiplieatioii. hy both diroct and 

 indiicet division, miist lead to the accumulation of a large num- 

 her of nuclei in each cell unless an opposite process, reducing 

 tlieir number takes 2)lace at the same tinie. 



An glance at a section of an older anthor will at once 

 sliow tliat no excessive accumulation of nuclei occurs in the cell 

 and 1 liave succeeded in linding clear evidence of a nuclear de- 

 generation taking place side by side \vith the nuclear niultipli- 

 cation. 



In iliis process the nuclear membrane, which stains very 

 deeply, becomes ruptured and shredded out into a group of fibres 

 or narrow laminae whilst the nucleolus can also, in many in- 

 stances, be seen to rosolve itself into a coarse fibre. 



Tliere can be little doubt tliat the groups of fibres formed 

 in this manner correspond to the structures which Meves^) has 

 recently described in the tapetal cells of Nymphaea alba and 

 which be has compared to the chondromiten of certain animal 

 cells. 



It is quite easy. in well hxed material, -j to hnd all stages 

 between a complete nucleus and one that is only represented by 

 a group of fibres. In Fig. 43, 44 and 45 d and f I have drawn 

 nuclei which are degenerating in this way. 



These fibres. of nuclear origen, become gradually more 

 numerous in older anthers, as the tapetal nuclei continue to di- 

 vide and to degenerate, but whether they all persist as fibres or 

 whether some of them are lost sight of in the course of further 

 changes I am unable to say. It is certain, however, that the 

 cytoj^lasm of the tapetal cells which are approaching disintegration 

 stains very deeply and that it contains a large number of these fibres. 



Just before tapetal disintegration the whole contents of the 

 cell, apart from the unaltered nuclei,^) break down into coarse 

 granules which stain intensely with iron-haematoxylin and these 

 become distributed among the ^^ollen grains when the cell loses 

 its individuality. 



Dirring the development of the anther starch apj)ears and 

 again disappears in the tapetum according to the conditions of 

 growth and this shows that carbohydrates are being employed 

 in metabolism. 



The conclusion which may be drawn from the above facts 

 is that a large part of the material which accumulates in the 

 tapetal cells during their development and which subsequently 

 passes into the pollen grains to replenish their exhausted proto- 

 plasts has at one time or another entered into the composition 

 of the tapetal nuclei und that there is here, therefore, a direct 

 relation between nuclear substance and cytoplasmic growth. 



^) Meves, Fr. „Über das Vorkommen von Mitocliondrien bezw. Chon- 

 dromiten in Pflanzenzellen." (Berichte d. Deutsch, bot. Gesell. XXII 1904. 

 pp. 284-286.) 



-) ATor cester's fluid is bj' far the best fixatine for this purpose. 



^) Wliich are two or three in number. 



