THE MEGASPORANGIUM 



nard 17 ) has. Among the Papaveraceae, Papaver orientate 

 (Vesque 12 ) has no parietal cell. Among Cruciferae, Capsella 

 (Guignard 17 ) has no parietal cell, but Alyssum (Miss Kid- 

 dle 42 ) has one that does not divide. Among the Leguminosae, 

 Orobus angustifolius (Guignard 16 ) is the only one recorded as 

 without a parietal cell; and among the Umbelliferae, Sium 

 has no parietal cell, but in the allied Araliaceae a parietal cell 

 is cut off (Ducamp 62 ). That Loranthaceae and Balanophora- 

 ceae have no parietal tissue is probably only a part of the ex- 

 tensive modification of their megasporangia. It is perhaps 

 noteworthy that the suppression of parietal tissue among Ar- 



FIG. 27. Ranunculus multifidus. Longitudinal sections of nucell us, x 475. A, single 

 archesporial cell (shaded) which is also the megaspore mother-cell, no parietal cell 

 being formed ; two of the epidermal cells above the archesporial cell show peri- 

 clinal divisions. B, second division of the megaspore mother-cell, by which four 

 megaspores are being formed. After CouLTER.* 8 



chichlamydeae is most extensively displayed by the Ranuncu- 

 laceae and its allies, rather than by the more specialized groups ; 

 but no generalization is safe until some knowledge of the gen- 

 eral conditions among the Umbelliferae and other high groups 

 of the Archichlamydeae is available. 



The strongest argument that suppression of the parietal 

 tissue of the mega sporangium is a strong tendency among An- 

 giosperms is that this condition is universal among the Sym- 

 petalae so far as investigated. 



The primary sporogenous cells do not divide to increase 

 the number of sporogenous cells, so that in the megasporangium 



