46 DICOTYLEDONS. [chap^ iv. 



1 6. It must always be borne in mind, however, that none 

 of these characters are absolute. They are always subject 

 to exception. So that plants which exhibit a departure from 

 the prevalent type of Dicotyledons in any single character 

 only are still referred to the same Class. Thus we have a 

 few Dicotyledons which are actually destitute of cotyledons, 

 or which have but one, or more than two ; we have some 

 with parallel-veined leaves, and others with the parts of the 

 flower in threes. But in all these cases the question as to 

 which Class the plant shall be referred, is decided, not by 

 any soHtary character, but by the sum or preponderance 

 of characters which it presents. 



The structure of the stem and mode of growth of the 

 wood we shall speak of in a later chapter. 



