86 REPRESENTATIVi: PLANTS 



are called rays or rai/ flowers. Why is such a name appro- 

 priate ? 



The second form is a tu])iilar, more or less elongated 

 structure, usually five-toothed at its upper end, and bearing 

 below, the structures named in the first form. From its 

 position those flowers are called disk flowers, and the whole 

 number combined is called the disk. Why are these terms 

 used ? 



Projecting from the top of the disk flower, or from near 

 the middle of the ray flower, are forked structures, com- 

 monly tightly inclosed in a yellowish enlarged part or 

 sheath. These two structures are the reproductive bodies 

 (pistil and stamens) of the flower, and they are considered 

 in detail in another place. 



The special flower. Study carefully the particular plant, 

 provided that it bears one or more heads of flowers. Learn 

 all that you can about the flower in its place of growth, 

 whether in a shady or open place, in water or swamp, ordi- 

 nary dry land or in very dry places, as sand or rock. These 

 several situations give rise to three diverse plant associ- 

 ations: the water-plants (Hydrophytes), ordinary plants 

 (Mesophytes), and very dry land plants (Xerophytes). Ob- 

 serve also whether the plants grow singly or grouped to- 

 gether in numbers. 



Compare the flower carefully with the statements made 

 above and determine the particular feature of the flower head. 



Drawings. Sketch, natural size, the head, face, and side 

 views, and name all the parts. 



Sketch a ray and a disk flower (m), one or both, accord- 

 ing to the flower. 



Sketch a bract of the involucre (in). 



Description. Describe carefully, noting the size, color, 

 odor, parts, and arrangement on the flower stem ; note also 

 the character of the leaves, their number and arrangement. 

 If present, observe and describe the root. 



