Butters: seeds and seedling of caulophyllum. 15 



part is somewhat narrower and about 120 mic. long-. The external 

 opening of the micropyle is situated at the bottom of the groove 

 which separates the stalk from the body of the ovule, the internal 

 opening is behind the nucellar cap. 



The embryo-sac is clavate, about 340 mic. long, 20 mic. in diameter 

 at the antipodal end, and 130 mic. at its widest portion. The wide 

 part of the embryo-sac has a very thin parietal layer of proto- 

 plasm surrounding a large vacuole. At the micropylar end the egg 

 apparatus forms a nearly spherical mass about 40 mic. in diameter 

 which projects strongly into this vacuole. The egg nucleus lies near 

 the inner end of this mass and is about 8 mic. x 16 mic. The synergids 

 lie at one side of the egg nucleus, and nearer the wall of the embryo- 

 sac. Their nuclei are very small, and their cytoplasm is vacuolate, 

 and is sharply distinct from the protoplasm of this embryo-sac. The 

 small antipodal portion of the embryo-sac is filled with cytoplasm 

 and contains the antipodal nuclei which are small and appear to be 

 on the point of breaking down. The primary endosperm nucleus is 

 large, and is located near the micropylar end of the embryo-sac. 



Fertilization was not observed although in several preparations 

 remains of the pollen-tube were seen within the micropyle. The 

 pollen-tube apparently enters the embryo-sac between the inner 

 integument and the nucellar cap. 



Development of the Seed after Flow^ering — The Integuments. 



The outer integument increases greatly in thickness, especially in 

 the chalazal region. The superficial cells of this integument become 

 specialized, their contents become somewhat denser, their outer 

 walls become thickened and a distinct cuticular layer is formed. The 

 cells of this epidermis undergo many anticlinal divisions as the 

 seed matures. In surface view they present somewhat irregular 

 outlines, and heavy vertical walls. This layer of cells forms the 

 tirm and waxy covering of the ripe seed. 



About a month after flowering, the form of the embryo-sac 

 begins to undergo a marked change due to the peculiar development 

 of the outer integument in the vicinity of the micropyle. The integ- 

 ument grows very rapidly in a ring-like area surrounding the 

 micropyle. The end of the embryo-sac becomes first flattened, and 

 then invaginated. This ingrowth of the integument increases until, 

 in the mature seed, it extends about one-third of the distance across 



