358 INTRODUCTION TO EMBRYOLOGY OF ANGIOSPERMS 



place by furrowing or by the formation of cell plates, and whether 

 the mode of division is successive or simultaneous. 



3. Development and organization of the pollen grain. Number and 

 position of the germ pores and furrows; adornments of the exine; 

 place of formation of the generative cell; number and shape of the 

 nuclei in the pollen grain at the time of its discharge from the 

 anther. 



4. Development and structure of the ovide. Number of integuments 

 and the alterations in structure which they undergo during the 

 formation of the seed; presence or absence of vascular bundles in 

 the integuments; shape of the micropyle, whether it is formed by the 

 inner integument, or the outer, or both; presence or absence of an 

 obturator. 



5. Form and extent of the nucellus. Whether it is broad and 

 massive or thin and ephemeral ; presence or absence of a hypostase ; 

 place of origin of the integument or integuments, whether close to 

 the apex of the nucellus or near its base; persistence or gradual 

 disappearance of the nucellus during seed formation. 



6. Origin and extent of the sporogenous tissue in the ovule. Nature 

 of archesporium, whether it is one-celled or many-celled; presence 

 or absence of wall layers ; presence or absence of periclinal divisions 

 in the cells of the nucellar epidermis. 



7. Megasporogenesis and development of the embryo sac. Arrange- 

 ment of megaspores; position of functioning megaspore; whether 

 the embryo sac is monosporic, bisporic, or tetrasporic; number of 

 nuclear divisions intervening between the megaspore mother cell 

 stage and the differentiation of the egg. 



8. Form and organization of the mature embryo sac. Shape of the 

 embryo sac and the number and distribution of its nuclei ; persistence 

 or early disappearance of the synergids and antipodal cells ; increase 

 in number of antipodal cells, if any; formation of embryo sac caeca 

 or haustoria. 



9. Fertilization. Path of entry of the pollen tube; interval be- 

 tween pollination and fertilization; any tendency toward a branch- 

 ing of the pollen tubes during their course to the ovule. 



10. Endosperm. Whether it is of the Nuclear, Cellular, or 

 Helobial type; orientation of the first wall in those cases in which 

 it is Cellular; presence or absence of endosperm haustoria and the 

 manner in which they formed if present; nature of food reserves in 



