AND THE Embryo-sac in Bignonia venusta 91 



side., However, around the ends of the boat-shaped archesporial 



The cells equivalent to the 



masses 



general tapetum, as well as those of the outlying wall layer, usu- 

 ally divide several times, Fig. 8, so that the terminal portions of 

 the archesporial layer are sunk deeper into the general tissue. 



The layer of cells on the inner surface of the archesporium 

 gradually differentiates itself into an inner tapetum, and here also 

 there are no further tangential divisions. 



The two general wall layers persist, and there is no fibrillar de- 

 velopment of the outer wall layer. At the time of dehiscence of 

 the anther, these layers are compressed, and the epidermis some- 

 what modified. According to the early work of Purkingc,* Mirbelf 

 and others the endothecium of these writers (final wall layer) is 

 always partially or wholly fibrous. The more extended study by 

 Chatin I upon developing, mature and dehiscing anthers In a large 

 number of orders demonstrated that this generalization could 

 not be made. Moreover, he found that the presence of fibrous 

 structures Is not at all dependent upon the natural position of the 

 order. Chatin distinguished three general classes in which no 

 fibrous layer occurred, as follows : 



" I. Que les cellules fibrcuses manquent, en general, dans les 

 antheres a dehiscence porlclde. 



"2. Que les cellules fibrcuses sont defaut dans un certain nom- 

 bre d'antheres a dchiscense longitudinale. 



"3. Que dans quelques plantes dont les etames paraissent 

 avoir subi un arret de developpement, sinon morphologique du 

 moins histologique, 1' absence de cellules fibrcuses coincide avec la 

 mauvaise conformation du pollen." 



Thus he found that among dicotyledons the fibrous tissue is 

 entirely absent in Mclastomaceae, Vacciniaccae, and Ericaceae. 



it is absent in members of such widely separated orders as 

 Tremandraccae {Tctrathecd), Caesalpinaceae {Cassia), Ebenaceae 



^Purkinge, J. E. De cellulis aiilhcrarum fibrosis, Vratislaviae. 1830. [Ref. " 

 Chatin J.] 



f Mirbel, Complement des observations sur le Marchantia, suivi de recherdies sur 

 la'm^tamorphose des utricles et sur Torigine, les developpements et la structure de Tan- 

 there et du pollen dans les vegetaux Phanerogames. Mem. de I'Acad. royale des Sci. 

 13: . 1835. 



J Chatin, A. De I'Anthcre, Paris. 1870. 



A train 



