62 



MORPHOLOGY OF ANGIOSPERMS 



A 



The archesporial cells behave as do those of the microspo- 

 rangium, ana in ease the archesporium is a plate of cells, the 

 resemblance is striking. In the large majority of cases, haw- 

 ever, the archesporium is a single cell, and often by transverse 

 division it gives rise to a primary parietal cell and a primary 

 sporogenous cell (Fig. 26). That the former cell, or plate of 

 cells, as it is in the case of a several-celled archesporium, repre- 

 sents the primary parietal layer of the microsporangium seems- 



clear. In recognition of this fact 

 Strasburger called it the " tapetal 

 cell," hilt for reasons given under 

 the microsporangium we shall call it 

 the parietal cell — that is, a cell that 

 develops in part the wall of the em- 

 bedded sporangium. Mottier 2S has 

 reported a very peculiar case in Ari- 

 saema, in which the single archespo- 

 rial cell divides by anticlinal walls 

 into three or four cells, each of which 

 then cuts off a parietal cell. Just 

 how far this is exceptional behavior 

 remains to be seen, but it intro- 

 duces an interesting problem as to 

 the application of the term archespo- 

 rium. 



The behavior of the primary 

 parietal cell is exceedingly varied. 

 An extreme case is for a series of 



sporial cell has given rise to pri- periclinal divisions to occur, result- 

 mary parietal cell (t) and pri- ■ _ • „ -i „ o ■ , ^ -,, 



1 ii , , m S ln a long row of parietal cells, 



mary sporogenous cell (m). — ° ° ' 



After Chambeklain.*" corresponding to the parietal layers 



of the microsporangium. In case 

 there is a plate of archesporial cells the radial rows of parietal 

 cells are very conspicuous, as in the Rosaceae and many of the 

 Amentiferae (Figs. 23, B, /), E). In other cases the parietal 

 rows become lost by the formation of anticlinal walls. If 

 the mother-cell broadens rapidly, the first divisions of the pri- 

 mary parietal coll may be anticlinal, followed by periclinal 

 divisions, as in Ruta graveolens (Guignard 17 ) and Potamoge- 

 ton foliosus (Wiegand 64 ). The deep-placing of the sporoge- 



Fig. 26. — Salix glaucophylla. Lon- 

 gitudinal sections of nucellus, 

 x 631. .4, single hypodermal 

 archesporial cell (a). IJ, arche 



