PISUM SATIVUM 



367 



Pultz (15) in his study of the deposition of starch in the seeds of 

 Pisum has followed the embryogeny from early stages to maturity. 

 Twenty-four hours after pollination, when the embryo is just 

 beginning to develop, there is an abundant accumulation of starch 

 which is strictly localized in the cells of the inner integument and 

 in those of the outer integument at the chalaza near the end of the 

 embryo sac. (Fig. 186, A.') At the end of thirty-six hours, the 

 young embryo is developing in the embryo sac near its micropylar 

 end, and by this time the endosperm occupies a peripheral position. 



int 



mxc- 



D 



Fig. 186. A-D, stages in development of ovule showing progressive deposition of starch, 

 represented by dots. A, ovule, 14 hours after pollination; B, same, 48 hours after pollina- 

 tion in which digestion of inner integument is beginning and a more general distribution of 

 starch is evident; C, young seed three days after pollination, showing complete digestion of 

 inner integument and presence of starch in outer integument ; D, young seed four and one- 

 half days after pollination, showing change in position of embryo and increased deposition 

 of starch; £, diagrammatic drawing of young embryo and suspensor : cha, chalaza; emb, 

 embryo ; end, endosperm ; i int, inner integument ; mk, micropyle ; int, outer integument ; 

 sus, suspensor. (Figures A-D after Pultz; E after Guignard, Ann. Sci. Nat.') 



Both the embryo and endosperm are devoid of starch at this stage, 

 but there is an increase in the starch in the inner and outer integ- 

 uments. (Fig. 187.) 



Between two and three days after pollination, continued growth 

 of the embryo results in the complete digestion of the nucellar 

 tissue and the beginning of digestion of the inner integument and 

 the starch which it contained. (Fig. i86, B.) At this stage, the 

 suspensor begins to elongate; and the embryo is pushed toward the 

 curved portion of the embryo sac where it ultimately completes its 

 development. Three to four days following pollination, the inner 

 integument is completely resorbed and the embryo sac is enlarged 



