GAMF.TOrnVTE A\D SPOROFHYTE. 



331 



is developing it derives its nourisliment from tlie endosperm (or 

 in some cases perhaps from the nueelhis). At the same time 



the 



Fertilization of cotton, 

 pollen tube ; Sii, synergids 

 egg. wHth male and female 

 cleus fusing, (Duggar.) 



integuments increase 

 in extent and harden as 

 the seed is formed. 



661. Perisperm. — In " 

 most plants the nucelhis is "' 

 all consumed in the de\e]- 

 opment of the endosperm, 

 so that only minute frag- 

 ments of tiisorganized cell 

 walls remain next the in- 

 ner integument. In some 

 plants, however, (the water- 

 lily family, the pepper 



Fig-3y6. 



Diagrammatic section of o\-ary and ovule at time 



faniilv, etc.,) a liortion of °^ fertilization in angiosperm. /, fiinide of ovule ; 



' ^ 11. nucellus ; vi , micropyle ; /'. antipodal cells of 



the nucellus remains in- embryo sac; ^, endosperm nucleus: X-. egg cell and 



synergids ; ai. outer integument of ovule; z'/. inner 

 tact in the mature seed, integument. The track of the pollen tube is shown 



down through the style, walls of the ovary to the 

 In such seeds the remain- micropylar end of the embryo sac. 



ing portion of the nucellus is the perisperm. 



662. Presence or absence of endosperm in the seed. — In 



many of the angiosperms all of the endosperm is consumed by 

 the embryo during its growth in the formation of the seed. This 

 is the case in the rose familv, cruciiers, composites, willows, oaks, 

 legumes, etc., as in the acorn, the bean, pea and others. In 

 some, as in the bean, a large part of the nutrient substance pass- 



