632. 



THE STRUCTURE OF ECONOMIC PLANTS 



Borthwick and Robbiiis (3) have investigated the anatomy of 

 the fruit and seed coat. In the young ovary, just prior to anthesis, 

 the nucellar tissue surrounding the megagametophyte is almost 

 entirely digested, and the massive integument of the single anatro- 

 pous ovule consists of from ix to 18 rows of parenchymatous cells. 

 The innermost layer is readily distinguishable from the others 

 because of the larger size of its cells. Even at this early stage, 



-pep 



-}--o ep 



emb s-'"! 



Fig. 3x9. A, transection of portion of ovary z hours after anthesis ; B, transection of akene 

 7 days after anthesis : emh, embryo ; emb s, embryo sac ; end, endosperm in which some wall 

 formation is still in progress ; i ep, inner epidermis of integument ; int, integument ; nls, disin- 

 tegrating cell of nucellus ; o ep, outer epidermis of integument ; pep, pericarp. (Redrawn 

 after Borthwick and Robbins, Hilgardia.') 



the integumentary parenchyma may give evidence of some dis- 

 integration. The pericarp varies in thickness and its cells resemble 

 those of the integument except that they are somewhat smaller. 

 There is a distinct outer epidermis; but, by the time anthesis 

 occurs, lysigenous cavities have begun to develop in the inner 

 portion of the pericarp, and disintegration of all except the outer- 

 most layers of the ovary wall proceeds rapidly. (Fig. 3x9, A.^ 

 A week after anthesis, there is further disintegration of the tissues 

 of pericarp and integument as the embryo enlarges and the endo- 

 sperm is formed. By the tenth day, the cells of the inner epidermis 



