THE STAMEN 



111 



may be divided longitudinally, and the separation extend down into the 

 filament, as in Alnus, Corylus, Ostrya, and some Malvaceae; each lateral 

 half, with its two sporangia, forms a pseudoanther. Greatly modified 

 forms of anther, frequent in some families, are associated with elaborate 

 methods of pollen distribution. 



The form of tlie connective determines, in large degree, the form of 



Fig. 51. Diagram representing main trends of specialization in stamens of the 

 Magnoliaceae. Cross sections through fertile parts show position of wall-less 

 sporangia and peripheral endothecial layer. A, Magnolia maingayi; B, M. nitida; 

 C, M. humori; D, Manglietia forrestii; E, Michelia fuscata; F, Magnolia hypoleuca. 

 {After CanrigJit.) 



the anther. In more primitive families, it constitutes a major part of the 

 anther (Fig. 49B, D to F, K, L), and the sporangia are minor struc- 

 tures; in advanced families, the connective is a slender median axis, 

 sometimes hardly more than a thread or point of attachment for the 

 prominent anther lobes. A series in progressive reduction exists from 

 the massive connective of the Magnoliaceae, TrocJwdcndron, and Tctra- 

 centron to the mere fragment of the Gramineae, where the connective 

 has been described as "absent." 



