,46 



on the innermost guide circle of his large sheet. (The student 

 should have previously drawn lightly the proper number of radi" 

 and circles to take care of the types to be offered.) It is well 

 to similarly assist the student with his second cycle until he 

 "catches" the idea. After that he goes it alone. Acquiring his 

 data from all possible sources he organizes it on his sheet where 

 he cannot escape "comparing the stages with those of preceding 

 types, with the delightful result that a goodly proportion of the 

 learners really " get the big idea " which is intended for them. 



The accompanying plate is the work of an unassisted student, 

 Mr, Fred B. Monroe. Above all it is important that the students 

 make this little chart ; for the instructor to make a large one (wall 

 chart size) to be used as a basis for mastering the situation would 

 be an unfortunate pedagogical error. 



A few comments on some of the desirable features may not be 

 out of place. Homologous structures are on the radii : Opposite 

 radii show contrasting conditions in the two generations, viz., 

 sporophyte vs. gametophyte ; fertilization vs. reduction ; sex 

 organs vs. sporangia, etc. ; on the right of the heavy diagonal line 

 sporophyte structures (2.r number of chromosomes) are dia- 

 grammed ; on the left gametophytic ones (x number of chromo- 

 somes). Passing outward along a radius gives a summary of 

 the evolutionary changes in that structure, the sporophyte and 

 gametophyte radii, of course, being of the most significance. 



In the higher land plants in which sporophyte and gametophyte 

 tissues remain together it is desirable to indicate this in the draw- 

 ings on some of the radii by carrying the structures over the di- 

 viding line between the generations, differentiating them from 

 each other by drawing one with dotted lines or handling them 

 with different colored inks. Further, as shown in the student's 

 diagram it is desirable to introduce the seed (or grain in the case 

 of corn) in its proper place, diagramming its parts and thus sum- 

 ming up the life cycle structures as they are actually "summed 

 up " in the seed. 



The plate as presented is by no means perfect and should not 

 be understood as showing all of the possibilities of the method. 



