426 INTRODUCTION TO EMBRYOLOGY OF ANGIOSPERMS 



triploicl lower polar nucleus, and the haploid male gamete, and is 

 therefore pentaploid (Fig. 216D,E). In Penaea and Plumbago 

 there are 4 polar nuclei so that here also the endosperm is penta- 

 ploid (Fig. 216F ,G). Still higher degrees of polyploidy are seen in 

 Acalypha indica and Peperomia (Fig. 216H ,1), and in one species 

 P. hispidula, as many as 14 nuclei fuse to form a secondary nucleus 

 which, after fusion with a male nucleus, gives rise to a 15n endo- 

 sperm (Fig. 216/). In Pandanus even the nuclei of nucellar cells 



Butomopsis 



Polygonum 



Fritillaria 



Plumbagella 



B 



Plumbago 



Acalypha indica 



D E 



Peperomia Peperomia hispidula 



F G H I J 



Fig. 216. Diagrams of embryo sacs of various plants, showing variations in the 

 number of nuclei fusing to form primary endosperm nucleus. In all cases, male 

 nucleus entering into fusion is shown in solid black. 



enter into the embryo sac and take part in the fusion, so that the 

 endosperm shows varying degrees of polyploidy. 



It is clear from the above that there is no uniformity in the 

 origin of the endosperm, and that whatever the number of polar 

 nuclei taking part in the fusion, the result is always a formless mass 

 of cells without any semblance of a second embryo and designed 

 solely to serve as a source of nutriment to the zygote. 



The participation of a male gamete in the fusion is, however, a 



