291 
Beer, Development of tlie pollen grain and anther of some Onagraceae. 
together upon tlie spindle so that it is not easy to count them. 
I have clistinguished 13 to 14 in some cases and tlie latter 
number will probably prove to be tlie correct one. 
Between tlie cells of tlie tetrad, wliicli results froni tliis 
division. Septa are developed wliich form an extension of tlie 
mucilaginous mother-cell wall. Like tlie latter tliese septa also 
give tlie reactions of callose (Figs. 10 and 11). 
Mangin 1 ) lias called attention to three delicate lines wliicli 
run tlirougli tke middle of tlie septa of tbe fnlly grown special- 
motlier-cell wall and join one another at tlie centre of tlie 
tetrad. 
He pointed out that tliese lines were often granulär in 
structure and he believed them to be nitrogenous in nature. 
Other authors have figured these radiating lines in the 
special-mother-cells of other plants; Strasburger figuring them 
both for Älthaea rosea and Gaura biennis as long ago as 1882 . 
I have observed these lines in all the Onagraceae wliicli I 
have examinecl. By careful focussing and by the comparison 
of series of microtome sections. I find these lines to be the 
optical expression of laminae. Most probably these laminae 
represent the first lamellae deposited after tlie completion of 
cell division. They differ somewliat from the rest of the 
special-mother-cell wall in their beliaviour towards stains but 
their reactions still indicate their callose composition (Figs. 12 
and 13). Moreover at a later stage, .when the special-mother- 
cellwall breaks down and the pollen 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 wliich are a little older we observe the first 
appearance of the pollen membrane round eacli 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 
tlie callose wall and even reagents wliich cause general plasmoly- 
sis and considerable distortion of the ceh-walls of the anther 
sei dom separate the very young pollen membranes from the 
special-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 thän it is to sepiarate tliis film from tlie 
callose wall. From the first, however, it can he distinguished 
from tlie special-mother-cell wall by its beliaviour towards rea¬ 
gents. It stains red with ruthenium red; it colours much niore 
deeply than tlie callose wall with bismarck brown, fuchsin, or 
methylene blue; it is unstained by corallin soda, and it becomes 
yellow or brown in clilor-zinc-iodine solution. 
9 Bull. Soc. Bot. d. France. T. 36. 1889. p. 391. Mangin described 
tliis in tlie special-motlier-cell wall of Altliciea rosea. 
