146 BOTANY. 



EXERCISE LXIV. 

 Characters of the Compositae. 



Dandelions, daisies, dahlias, thistles, etc., we see, are 

 composed, of many florets, inclosed in a calyx-like in- 

 volucre. Plants of this kind have, therefore, been named 

 Compositae, from the compound, or composite, nature of 

 what, to the untaught, seems a single flower. They form 

 one of the most numerous, and, at the same time, one of 

 the most natural and perfect families in the vegetable 

 kingdom. There are about nine thousand different species 

 included in it. They are found in all countries and cli- 

 mates. About \ of the plants of North America, and \ of 

 all tropical plants, belong to it ; indeed, from ^ to -^ of all 

 the plants in the world are of this order. 



Now, why is this order said to be very natural ? Why, 

 for instance, is it a more natural group than the rose 

 family ? If examples of all these nine thousand species 

 were brought together, they would be seen to have one 

 conspicuous and many important characters in common. 

 In every one of them the inflorescence is a dense head, 

 inclosed in a more or less compact involucre. But, when 

 you have collected all the members of the rose family, 

 you do not see so many features common to all, nor any 

 marked one which stamps them as similar. On the con- 

 trary, in all their prominent characters, they are often 

 widely unlike, and only experienced botanists can detect 

 their affinities. 



It must not be supposed, however, that all plants with 

 flowers in a head belong to the Compositae. The case is 

 not quite so simple. Plants are not to be classified by a 

 single character. We must not forget the principle that 

 characters of cohesion and adhesion in the flower are of 

 the first importance in determining affinities. 



Now, what are the characters of cohesion and adhesion 

 in which the florets of all the plants named in Ex. LX 



