236 THE TEACHING BOTANIST 



most essential things first, is the best rule. Terms for the 

 principal parts - - perianth, petals, sepals, etc. and for the 

 conditions of union of parts, -- gamopetalous, gamophyllous 

 (for parts of a perianth), etc. - -should be given after the need 

 for them has been felt. 



The construction of the diagrams is the most important 

 pedagogical part of this exercise. They will be spoken of 

 below. 



In the morphology, the students should of themselves recog- 

 nize that receptacle is stem which remains short, that petals 

 and sepals are leaves ; but stamen and pistil, particularly 

 anthers and ovules, will puzzle them. They should be 

 allowed, or, if necessary, led to see that the latter are not 

 homologous with anything they have yet studied ; in fact, so 

 far from representing modified edges of leaves, etc., they are 

 as distinct from leaf or stem as these are from root, and they 

 are older than the leaf or the stem (see page 146). They 

 are sporangia containing spores, an inheritance from the non- 

 flowering plants, with certain appendages added. The ovule 

 (nucellus) is a spore-case containing a single spore (macro- 

 spore or embryo sac) whose germination produces the egg- 

 cell, the whole surrounded by one or two protective coats. 

 The anther is a spore-case containing spores (microspores or 

 pollen-grains) whose germination produces ultimately the 

 pollen tube with its contents. The pistil is composed of in- 

 folded leaves with the spore-cases on their edges. It is a mis- 

 take to try to homologize the ovary, style, and filament, with 

 blade or petiole of a leaf, for the differentiation into blade and 

 petiole is an attribute of the foliage leaf only, not of the spore- 

 bearing leaves, which, it is possible, have not been derived at 

 all from foliage leaves (see page 147). I have found it in 

 my own experience most profitable to teach the correct mor- 



