128 



A TEXT-BOOK OF BOTANY. 



able to give particular attention to the morphology of this group, 

 as also to the distinguishing characters of a number of the impor- 

 tant families. 



Economic Importance. As indicating the great usefulness to 

 mankind of the products obtained from the Angiosperms it will be 

 sufficient to merely mention that all of our garden vegetables as 



FIG. 84. Development of embryo in the shepherd's purse (Capsella Bursa-pastoris). 

 I -VI, various stages of development: Vb, apex of the root seen from below, i, i, 2, 2, the 

 first divisions of the apical cell of the pro-embryo (suspensor); h, h, cells from which the 

 primary root and root-cap are derived; v, the pro-embryo; c, cotyledons; s, apex of the 

 axis; w, root. After Hanstein. 



well as the great crops of cereals like wheat, corn, rye, etc. ; edible 

 fruits and seeds ; textile products, such as cotton, flax, etc. ; medic- 

 inal products ; timbers of various kinds, as oak, mahogany, walnut, 

 chestnut, cherry, etc., are furnished by this great group of plants. 



EVOLUTION. 



Contrary to a popular opinion, the idea of evolution is almost 

 as old as the human race. From the time when man began to 

 think about the things around him he could not help but see that 



