Beer, Development of the poUen grain and anther of some Onagraceae. 291 



together upon the spindle so tliat it is not easy to connt thom. 

 I have distinguislied 13 to 14 in some cases and the latter 

 number will probably prove to be the correct one. 



Bet^een the cells of the tetrad, \vhicli results from this 

 division. Septa are developed which form an extension of the 

 mucilaginous mother-cell wall. Like the latter these septa also 

 give the reactions of callose (Figs. 10 and 11). 



M angin ^1 has called attention to three delicate lines which 

 run through the middle of the septa of the fully grown special- 

 mother-cell wall and join one another at the centre of the 

 tetrad. 



He pointed out that these lines were often gi'anular in 

 strncture and he believed them to be nitrogenous in nature. 



Other authors have tigiired these radiating lines in the 

 special-mother-cells of other plants: Strasburger figuring them 

 both for ÄltJmea rosea and Gaura biennis as long ago as 1882 . 



I have observed these lines in all the Ouagyaceae which I 

 have examined. By careful focussing and by the comparison 

 of series of microtome sections. I find these Hnes to be the 

 optical expression of laminae. Most probably these laminae 

 represent the first lamellae deposited after the completion of 

 cell division. They differ somewhat from the rest of the 

 special-mother-cell wall in their behaviour towards stains but 

 their reactions stiU indicate their callose composition (Figs. 12 

 and 13). Moreover at a later stage, when the special-mother- 

 cellwall breaks down and the poUen grains are liberated, these 

 lamellae remain behind for some time unchanged and continue 

 to give a very characteristic callose reaction with corallin-soda 

 (Figs. 51 and 52). 



In anthers which are a little older we observe the first 

 appearance of the pollen membrane round each special- 

 mother-cell. 



AVe first recognise it as a very delicate film lining each 

 cell-cavity of the tetrad. It is in most intimate contact with 

 the callose wall and even reagents which cause general plasmoly- 

 sis and considerable distortion of the cell-walls of the anther 

 seldom separate the very young poUen membranes from the 

 sj)ecial-mother-cell wall. The protoplast of the cell is also firmly 

 attached to the new membrane but it is easier to tear away the 

 cytoplasm from it than it is to separate this film from the 

 callose wall. From the first, however, it can he distinguished 

 from the special-mother-cell wall by its behaviour towards rea- 

 gents. It stains red with ruthonium red; it colours much more 

 deeply than the callose wall with bismarck brown, fuchsin, or 

 methylene blue; it is unstained by corallin soda, and it becomes 

 yellow or brown in chlor-zinc-iodine Solution. 



1) Bull. Soc. Bot. (1. France. T. 30. 1889. p. 391. Maugiu described 

 tliis in the special-mother-cell wall of Altliaai roxea. 



