THINGS ESSENTIAL TO BOTANICAL TEACHING 57 



materials under those trained in them. There is inher- 

 ently no more reason why they should be dragged into 

 scientific laboratories than into mathematics or athletics. 

 We shall now consider, more specifically, good pro- 

 cedure in the botanical laboratory itself. The arrange- 

 ment and equipment of the laboratory room and the 

 use of outlines, note-books, etc., are considered in later 

 parts of this book. The number of students in one 

 laboratory division should not, at the most, exceed 

 twenty-five or thirty, unless an assistant is available, 

 when it may be larger. Two-hour periods are the best 

 for beginners. Students do not become weary in that 

 time, and shorter periods are uneconomical on account 

 of the time lost in getting the work started and things 

 put away at its completion. The amount of work laid 

 out for each period may best be adjusted to rather 

 above the average student ; and more exact and 

 detailed work may be expected from the best members, 

 while the poorer must be permitted to do it much less 

 completely and perfectly. In each new laboratory 

 period all students should start the new topics together, 

 uncompleted work of earlier periods being made up in 

 time outside of regular hours, for which, as well as for 

 extra voluntary work, the laboratory should always be 

 open. The actual laboratory work is best managed on 

 the practicum plan, that is, the students are all working 

 upon the same problems or approximately so, and the 

 teacher goes about among them, giving individual en- 



