PREFACE. 



VU 



that complete examples should be gathered, completeness be- 

 ing determined thus : all small plants should be entire, root 

 and branch ; while of larger ones portions as ample as may be 

 manageable (if for an herbarium, nearly as long as the paper 

 used, or such as can while fresh be readily folded to the length 

 of the paper) must be selected, showing all the parts, — roots 

 if conveniently obtainable; perfect leaves, both root-leaves 

 and stem -leaves, if they differ at all, as they often do ; and 

 flowers including buds and old flowers with advanced fruits. 

 Sometimes perfect fall-grown fruits or seed-vessels are indis- 

 pensable, and, as they are always desirable, they should always 

 if possible be gathered. Furnished with such materials as 

 these, and supposing ourselves occupied with them at any pe- 

 riod of the pleasant springtide, let us look at p. 22 and p. 27, 

 wherein the two great divisions of plants are indicated. These, 

 it will be seen, consist of plants with parallel-veined leaves and 

 those with net-veined leaves. It is not generally difficult to 

 decide between these, for we may leave out of sight the very 

 few exceptions to the general rule that occur. Supposing our 

 plant is a Wallflower, it will be net- veined, and therefore exo- 

 genous. Now among the exogenous plants it will be seen 

 that there are some polypetalous (the Thalamiflores and Caly- 

 ciflores), some monopetalous (the Monopetals), and some 

 apetalous or without petals (the Monochlamyds) . It will at a 

 glance be ascertained that this flower has petals as well as 

 calyx, and more than one petal, so that it must be polypeta- 



