54 SEEDS AND SEEDLINGS. 



discharged one or other of the first two. The four types 

 of seedling are then those in which (1) the cotyledons merely 

 store food, (2) the cotyledons serve only as digesting and 

 absorbing organs, (3) the seed is non-endosperniic, but the 

 cotyledons besides containing some food come up into the air 

 and make more food, (4) the seed is endosperrnic and the 

 cotyledons first digest and absorb the endospermic food and 

 then come out of the seed and make food. Examples have 

 already been given of the four types. 



91. Monocotyledons and Dicotyledons. Of the 



we have studied, Maize, Wheat, Onion, and Date belong to 

 the class of Seed-Plants known as Monocotyledons, while all 

 the others (except Pine) belong to the larger class of the 

 Dicotyledons. This apparently trivial difference is, on the 

 whole, so absolutely constant, and goes along with so many 

 other differences, that it was long ago recognised as a basis 

 for dividing up the higher Seed- Plants into these two groups. 

 A general statement often made is that while most Dicoty- 

 ledons have non-endospermic seeds, all Monocotyledons have 

 endosperm, but this is wrong. As a matter of fact, there are 

 many Monocotyledons which have no endosperm in their 

 seeds, or very little, and probably half of the known species 

 of Dicotyledons have endospermic seeds. 



92. The Early Foliage-Leaves of Seedlings. You will 

 notice, in your studies of seedlings, that in many cases the first 

 foliage-leaves, above the cotyledons, are simpler in form than 

 the later or "adult" leaves. G-ood examples are seen in 

 Broad Bean, French Bean, Scarlet Runner, and Pea, which 

 have already been mentioned ; " Nasturtium " (Tropaeolum) , 

 whose early leaves have the stalk inserted in the ordinary way 

 at the edge of the lobed blade, but the later leaves have the 

 stalk inserted at the middle of the underside of nearly circular 

 blade ; Gorse, whose early leaves are three-lobed, while the 

 later ones are simple, narrow, and pointed. Look for other 

 examples of this interesting feature, which is usually held 

 to be a case of the individual repeating, or recapitulating, in 

 its own development the stages through which its ancestors 

 passed in the course of evolution. 



