266 THE TEACHING BOTANIST 



to go. At these times materials may be gathered for the 

 structural herbarium earlier recommended (page 109). When 

 analysis work is undertaken, it is better done in the field ; for 

 which purpose the students take their manuals (for which the 

 leather-bound field editions should be used) with them. In 

 this work every effort should be exerted to make them 

 acquainted with families as well as with species. Each plant 

 studied should be made to contribute not only its own name 

 and systematic position, but should also make firmer and 

 clearer the students' knowledge of the larger groups, so that 

 the whole scheme of classification will come to stand out as 

 a sort of unified structure in his mind. 



A genealogical tree, such as is called for under Exercise 100, 

 would be about like that on the preceding page (Fig. 29). 

 The mode of branching indicates the supposed mode of origin 

 of the groups from one another ; thus the Algae were once 

 the main line, from which the Bryophytes came off as a side 

 branch, soon, however, themselves assuming the main line, 

 while the Algae became a side branch. The Mosses are a 

 side branch from the Liverworts. The Pteridophytes came 

 off as a side branch from Bryophytes, but soon took the main 

 line, and so on, as expressed in the diagram. 



