150 BOTANY. 



four petals. There is no cohesion in any of these flowers, 

 unless you except the spuriously syncarpous pistil (Fig. 

 349) . They are also without adhesion. I do not know 

 how successful you may be in observing the embryo, but, 

 with a good magnifying-glass, you should be able to see 

 that the radicle is folded upon the cotyledons, sometimes 

 against their edges, sometimes against the back of one, 

 but always folded. Now, these invariable features are the 

 ordinal characters of the Cruciferae. You may identify any 

 one of the sixteen hundred known species by the three feat- 

 ures first named, and, when you have done this, you may 

 safely infer the existence of all the others. You are en- 

 abled to do this because botanists have carefully studied 

 and analyzed these plants, and in every case, along with a 

 cruciferous corolla, tetradynamous stamens, and bractless 

 inflorescence, the other features have invariably been found. 

 Compare the characteristics of any order of plants, as given 

 at the beginning of the Flora, with the characters of that 

 order given in connection with its genera and species in 

 the body of the Flora. In the same way, if any plant have 

 certain ordinal characteristics, you may infer the other or- 

 dinal characters. 



I wish to say a word about the importance of the char- 

 acters by which you determine whether a plant is or is not 

 a crucifer. Some of you may think it strange that such 

 features as the length of stamens and the absence of bracts 

 should be named in describing an order of plants. These 

 points of . structure would not be looked upon as ordinal 

 characters but for one circumstance, to be carefully 

 borne in mind. It is their constancy, which here gives them 

 value. They take rank from their permanence. Perma- 

 nent or constant characters, no matter how trivial other- 

 wise considered, are of high value in classification. 



Order II of Chart I exhibits the characters of the Cru- 

 ciferae as here described. 



