21/ THE PLANT WORLD. 



the cotyledons are raised above the soil, describe any changes you 

 can see in their appearance. Are they opposite each other? Is 

 the stem any bigger below the cotyledons than above them ? Are 

 there any leaves below the cotyledons? Do the cotyledons begin 

 to shrivel up? What do you think makes them do so? 



The Leaves. — Observe the first leaves above the cotyledons. Is 

 there is a distinct leaf stalk and a broad, thin, flat blade f Do you 

 find any szcclUiig at any place on the leaf stalk? If so, where? 

 If possible examine plants that have grown in a window. Have 

 the leaves turned toward the light? If so, where did the bending 

 take place ? The tip of the blade is the apex, the place where the 

 blade joins the leaf stalk is the base of the blade? Can yovi find 

 two little wing-like parts on the leaf stalk at the base of the blade ? 

 Are there any where the leaf joins the stem? Is there a joint 

 in the leaf stalk at this place ? 



Does the stalk extend up through the blade toward the apex, 

 forming a midrib F Does the midrib branch into reins? Can 

 vou see an unbroken line of vein extending around the blade par- 

 allel to its edge? Of what advantage is this to the leaf? How 

 can you tell the upper from the under side of the blade? What 

 purposes do you think the veins serve? Are the two opposite 

 first leaves alike? ^lake labeled drawings. 



The other leaves above the first pair are conipound leaves 

 How many blades has each? Each of these blades is a leaflet. 

 Has each leaflet a stalk? Is there a joint where each leaflet joins 

 the leaf stalk? Does each leaflet have a pair of little leaf-like 

 bodies near the base of its blade ? Is there a pair also where the 

 stalk joins the stem? Is there a joint in the stalk at this place? 

 Are the stalks of the lower leaves longer or shorter than those of 

 the upper ones ? If the lower stalks were shorter could the lower 

 blades get the sunlight as well? If the upper blades were not 

 divided into three leaflets, would they shade the lower leaves more 

 than now ? ]\Iake labeled drawings and write descriptions. 



The cotyledons have shrivelled because the food that made them 

 thick has gone to nourish and feed the growing seedling. The 

 first leaf of the bean is not a true simple leaf. It is what is known 

 as a iinifoliate compound leaf, that is, a compound leaf with only 



