THE EMBRYO AND SEEDLING 



133 



intervals between leaves being much shorter in green- 

 houses than in places where there is any marked alterna- 

 tion of wet and dry seasons. 



After the young plant has reached an age of five or 

 six years the leaves begin to appear in crowns; at first 



71 



Figs. 71-73. — Dioon edule: early stages in the development of the 

 seedling: Fig. 71, coleorhiza breaking through the stony seed coat and 

 tip of root breaking through the base of the coleorhiza; Fig. 72, later 

 stage, showing tip of first leaf emerging between the two cotyledons; 

 Fig- 73 > the root is well developed and three leaves are seen between 

 the two cotyledons. Natural size. 



there are only a few leaves, perhaps only two or three 

 in a crown, but as the plant gets larger the number of 

 leaves in a crown gradually increases, until it reaches the 

 approximate number characteristic of the species. 



The leaves of seedKngs differ decidedly from those 

 of the adult plant. Naturally they are smaller, the first 



