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WEED FX,OEA OF IOWA 



Fig. 486. Development of the ovule and embryo of the Shepherd's Purse 

 (.Oapaella). A, young ovule, showing origin of two Integuments at base 

 of nucellus, n. B, outer integument growing beyond the inner, and the 

 ovule beginning to bend over ; es, embryo sac. C, diagram of a later 

 stage with mature embryo sac. D, development of the suspensor s. E, 

 early division of the terminal cell (embryo cell). F, later stage, showing 

 the differentiation of an outer cell layer In the embryo, which is to be- 

 come the epidermis. G, the two cotyledons c and the root region r now 

 clearly defined. H, lengthwise section of an ovule, showing the position 

 ■of an embryo in an embryo sac ; em, embryo ; s, suspensor ; e, endosperm ; 

 11, inner integument ; oi, outer integument ; m, mioropyle. 

 (A, B. C, adapted after Campbell. Ginn & Co.) 



