62 



MORPHOLOGY OF ANGIOSPERMS 



The archesporial cells behave as do those of the microspo- 

 rangium, and in case the archesporium is a plate of cells, the 

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

 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," but 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 25 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- 

 B rium. 



fiQ.^.SalixglaucopJiyiia. Lon- The behavior of the primary 



gitudinai sections of nuceiius, par i e tal cell is exceedingly varied. 



x 631. A, single hypodermal . .,,.,, 



archesporial cell (). , arche- An ^ extreme case is for a series of 

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



rnary parietal cell (t) and pri- j in & } rQW of parietal cellg 



mary sporogenous cell (m). c . 



After CHAMBERLAIN.* 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, #, D, 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 cell may be anticlinal, followed by periclinal 

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

 ton foliosus (Wiegand 54 ). The deep-placing of the sporoge- 



