62 INTRODUCTION TO EMBRYOLOGY OF ANGIOSPERMS 



ning of the series, the nucellus comprises a single layer of cells (the 

 epidermis) surrounding the archesporium (Fig. 4:4 A). This is in 

 accordance with the general condition in the Sympetalae. In Bou- 

 vardia and Vaillantia, which represent the next stage, the nucellar 

 epidermis is reduced to a few cells lying immediately above the 

 sporogenous tissue (Fig. 44B,C). In Rubia olivieri there is further 



A B 



Fig. 43. Young ovules of Orchis maculatus (A) and Aeginetia indica (B). Note 

 that in Orchis the integuments arise near base of megaspore mother cell, while in 

 Aeginetia the single integument arises near apical end of nucellus. (A, after Hage- 

 rup, 1944,' B, afar Juliano, 1935.) 



A B C D E F 



Fig. 44. Diagram illustrating different types of nucelli found in the Rubiaceae. 

 A, Phyllis. B, Bouvardia. C, Vaillantia. D, Rubia. E, Oldenlandia. F, Hous- 

 tonia. {After Fagerlind, 1937.) 



