THE EMBRYO 



193 



Treub 18 for Listera ovata and Epipactis palustris, and by 

 Leavitt 73 for certain species of Goodyera and Spirantlies. It 

 should be noted, however, that in Lemna (Caldwell 54 ), the 

 reduced aquatic ally 

 of the Araceae, a mul- 

 ticellular suspensor is 

 formed, the embryo 

 resembling the Lili- 

 um type described be- 

 low. 



Among the Lilia- 

 ceae a third type of 

 embryo - formation 

 seems to prevail. After 

 the first segmentation 

 of the fertilized egg, 



which is transverse, ^^^ /p. 



the subsequent divi- ' 



sions are very irregu- 

 lar, being transverse, 

 oblique, or longitudi- 

 nal in either cell, re- 

 sulting in a massive 

 proembryo. The dif- 

 ferentiation into em- 

 bryo and suspensor is 

 late and irregular, the 

 suspensor being mass- 

 ive, and inclined to 

 continue active divi- 

 sion until the end of 

 the embryo-sac is oc- 

 cupied by a spreading 

 suspensor tissue (Fig. 85). This is characteristic of Lilium 

 (Coulter 44 ), Erythronium (Schaffner 72 ), Tulipa (Ernst 69 }, 

 and probably all the allied forms, and the meristematic activity 

 of the suspensor is apt to result in polyembryony (see below). 

 Just how far this Lilium type of embryo is represented among 

 Liliales must be determined by future investigation, but it is 

 distinct enough to deserve separate mention. 



FIG. 85. Lilium philadelphicum. A, proembryo of 

 two cells ; x 300 ; B, middle cell of filament of 

 three cells has divided longitudinally; x 175; (7, 

 young embryo showing massive suspensor ; x 300 : 

 Z>, older embryo, showing different form of sus- 

 pensor ; x 300. After COULTER.** 



