THE FEMALE GAMETOPHYTE 



139 



ported more frequently in embryo sacs is that they are not very 

 distinct in the usual balsam mounts, and very few workers take the 

 trouble of removing the coverslip and testing the sections with 

 an iodine solution. 



While reference must be made to Dahlgren's papers for fuller 

 information on the subject, a few noteworthy cases of the occur- 

 rence of starch grains in the embryo sac may be mentioned here. 



E 



Fig. 90. Development of ovule and embryo sac of Leiphaimos spectabilis. 

 Oehler, 1927.) 



(After 



In Arachis (Reed, 1924), Tilia (Stenar, 19256), Pentstemon (Evans, 

 1919), and Acacia (Newman, 1934) the embryo sacs are so full of 

 starch that it becomes difficult to study the nuclei inside them. 

 In Styphelia (Brough, 1924) starch grains are so abundant in the 

 vicinity of the egg that the latter is obscured by them. In Den- 

 drophthora (York, 1913) their crowding is said to cause a degenera- 

 tion and disappearance of the nuclei. 



The stage at which the starch makes its appearance in the embryo 

 sac varies in different plants. In Loranthus pentandrus, Treub 

 (1883) saw starch grains even at the megaspore mother cell stage; 



