TBM COMPOSITOUS TBIBJSS 177 



some compositous flowers the florets are reduced 

 to two or three, or even to one! 



Suggestions.— Is the bud at the right in Fig. 171 a flower 

 closed up, or one which has not yet opened ? Are the stems of 

 the dandelions which bloom first in the spring shorter than those 

 which bloom later ? Do the flowers close at night and in dull weather ? 

 How long a period of sunshine is necessary to open the flowers ? 

 Does a flower open more than once ? Does the head (or involucre) 

 ever close up after it has gone to seed ? What time is required 

 for the flower stem to straighten up and to reach its full height ? 

 How many rows of bracts or scales are in the involucre ? Do the 

 positions of these bracts change from flowering-time to seeding- 

 time ? How far may a dandelion seed travel in the wind ? Do 

 dandelion plants vary much in size and shape of leaves (compare 

 Fig. 172) ? Is the variation associated with vigor of plant, richness 

 and moisture of soil, or other conditions ? At what seasons are 

 dandelions most abundant ? Do they ever bloom in fall or winter ? 

 How long does a dandelion plant live ? Upon what kind of soil 

 does it thrive best ? 



XXXIII. THE COMPOSITOUS TRIBES 



201. A rudbeckia, or yellow ox-eye daisy^ is a 

 common plant in pastures and meadows. It has 

 rough and hairy stems and leaves. A flower of 

 it is shown in Fig. 173. The central part of the 

 flower is high and cone-shaped, and a cross -section 

 of it shows that the receptacle, e, is really a 

 much -shortened stem, with flowers along its side. 

 In other words, the receptacle in compositous 

 flowers is the rachis of a condensed spike, and 



M 



