LACTUCA SATIVA 



635 



to retard gas exchange; since, when all of the pericarp, seed coat, 

 and endosperm are removed from seeds, the naked embryos initiate 

 growth within 14 hours. In cases where only the pericarp and 



— cot 



--eel 



-Ix d 



Fig. 332.. Longisection through epicotyl and cotyledonary node of six-day seedling 

 showing development of first foliage leaf and presence of lactiferous ducts. Cortical lactifer- 

 ous ducts which occur in seedling axis are not shown in this plane, variety New York Regular : 

 cot, cotyledon; eel, growing point of epicotyl; hyp, hypocotyl; /, first foliage leaf; Ix d, 

 lactiferous duct. 



outer portions of the seed coat were removed, so that the embryo 

 remained enclosed by the endosperm and the integumentary 

 membrane, Borthwick and Robbins found no germination at 30° C. 



