32 



MORPHOLOGY OF ANGIOSPERMS 



The development of the microsporangia began to be de- 

 scribed bv Xiiii'eli 2 in 1842, and was continued bv Hofmeister 3 

 in 1859-'61 ; but the first detailed account from the standpoint 

 of modern morphology is that of Warming 8 in 1873, which has 

 been made the basis of all subsequent accounts. This was sup- 

 plemented in 1876 by Engler, 9 and since then numerous inves- 

 tigators have added extensively to the literature of the subject. 



The anther at first is a homogeneous mass of small meriste- 

 matic cells covered by an epidermis (Fig. 9). Very early it 



Fig. 9. — Development of the mierosporangium. A-D, Doronicum macrophyllum : A, 

 transverse section of very young anther, showing primary sporogenous cell (a) and 

 primary parietal cell (b) ; B, slightly older stage ; C\ longitudinal section of anther in 

 same stage as that shown in B ; I>, later stage ; a, sporogenous cells. E< Menyanth, t 

 trifo/iata, transverse section of a microsporangium at a still later stage showing 

 tapetum (t) and microspore mother-cells (sni). F, Mentha aquatica, transverse sec- 

 tion showing tapetum (t) and sporogenous cells (a). — After Warming, from Goebel's 

 Outlines of Classification and Special Morphology. 



becomes faintly four-lobed in cross-section, and the differentia- 

 tion of the vascular strand of the connective outlines the gen- 

 eral plan of the structure. The whole hypodermal layer of 

 cells, representing the outermost layer of the periblem, is prob- 

 ably to be regarded as archesporial in its possibilities, and one 

 region of it is just as likely as another, under similar condi- 

 tions, to develop into actual archesporial cells. The favorable 

 conditions for this development, however, are under the lobes : 

 so that almost simultaneously with their appearance, a plate 



