LECTURE XXVII. 



THE first leaves formed on the young sporophyte are usually called 

 its cotyledons. In the Gymnosperms a variable number of these 

 (always exceeding one) arise in a circle surrounding the apex of the 

 stem. In the greater part of the Angiosperms there are just two 

 seed-leaves which arise as lobes on the embryo at opposite sides of 



-F 



C 



Col. 



FIG. 84. Seedling Dicotyledon. Two FIG. 85. Seedling Mono- 



seed leaves (cotyledons) at c. (From cotyledon, c, first leaf to 



Farmer's Practical Introduction to the emerge from the seed 



Study of Botany.) leaving the single cotyle- 



don still enclosed. (From 

 Farmer's Practical Intro- 

 duction to the Study of 

 Botany.) 



the groove, from which the apex of the young embryo's stem 

 differentiates. In their position they resemble those of the Gymno- 

 sperms but to all intents and purposes their number is fixed at two. 

 Besides these, there is an important section of the Angiosperms in 

 which the embryo develops first as a club-shaped mass at the lower 

 end of the suspensor and the distal half of this mass differentiates 



239 



