1406 



A TEXTBOOK OF THEORETICAL BOTANY 



TYPE 



Monosporic 

 8-nucleate 

 Polygonum type 



Monosporic 

 4-nucleate 

 Oenothera type 



Bisporic 

 8-nucleate 

 Allium type 



Tetrasporic 

 16-nucleate 

 Peperomia type 



Tetrasporic 

 16-nucleate 

 Penaea type 



MEGASPOROGENESIS 



Megaspore 

 mot/ier cell 



Tetrasporic 

 16-nucleate 

 Drusa type 



Tetrasporic 

 8-nucleate 

 Fritillaria type 



Tetrasporic 

 8-nucleate 

 Plumbagella type 



Tetrasporic 

 8-nucleate 

 Plumbago type 



Tetrasporic 

 8-nucleate 

 Adoxa type 



Division 

 I 



Division 

 II 



MEGAGAMETOGENESIS 



Division 

 III 



Division 

 IV 





 V® ®^ 



Division 

 V 



Mature 

 embryo sac 



Fig. 1300. — Tabulated diagram of developmental stages of the principal embryo sac 

 types. See text for details. (After Maheshzcari.) 



cell division, and these divide again once, to form eight nuclei which are 

 normally arranged. This is the type to which the familiar embryo sac of 

 Lilium was formerly supposed to belong. The true history in Liliurn is 

 more complex and conforms to the next type described. The present type 

 is much less common. It is a regular feature only in Adoxa and Sambucus 

 and occurs in some species of Ulmiis, Tulipa and Erythronium. 



5. Tetrasporic, eight-nucleate sacs. The Fritillaria type. This generic 



