THE MICROSPORANGIUM 



29 



soon becomes slightly four-lobed, and rows of hypodermal cells 

 become differentiated in each lobe by their larger size, radial elon- 

 gation, and more conspicuous nuclei. These form the archespor- 

 ium. The extent of the archesporial tissue varies considerably both 

 lengthwise and breadthwise. Either a single archesporial cell may 

 be seen in each lobe in a cross section of the anther, as in Sanse- 

 vieria (Guerin, 1927), Dionaea (Smith, 1929), and Boerhaavia (Ma- 

 heshwari, 1929), or a plate of such cells, as in Ophiopogon (Mahesh- 

 wari, 1934), Urginea (Capoor, 1937a), and most other plants. In 

 longitudinal section also the row may comprise only one cell as in 



Fig. 24. A-E, differentiation of parietal and sporogenous tissue in anthers of 

 Chrysanthemum leucanthemum (e = epidermis; end = endothecium ; m = middle 

 layer; t = tapetum; sp = sporogenous cell). (After Wanning, 1873.) 



Enalus (Kausik, 1941), or two cells as in Boerhaavia (Maheshwari, 

 1929), or several cells as in Urginea (Capoor, 1937a). 



Figure 24C-E shows the stages leading to the origin of the sporog- 

 enous tissue. The archesporial cells divide to form a primary 

 parietal layer toward the outside and a primary sporogenous layer 

 toward the inside. The cells of the former divide by periclinal and 

 anticlinal walls to give rise to a series of concentric layers, usually 

 three to five, composing the wall of the anther. The primary sporog- 

 enous cells either function directly as the spore mother cells or 

 undergo further divisions to form a larger number of cells. 



