262 THE TEACHING BOTANIST 



93. Prepare a synoptical essay, not over two hundred 

 words, upon the Gymnosperms, emphasizing 

 their ecology and relationships. 



Materials. Male and female flowers of the Pines may be 

 obtained in June and kept in formaline ; along with the young 

 stages should be collected some of the year-old cones. 



Pedagogics. This group is important but not easy to study 

 fully. It is easy enough to study the male flowers of Pine, 

 in which the homology of the anthers and pollen should be 

 kept plain by calling them microsporangia and mis'crospores. 

 In the female flowers it is very difficult to make out parts of 

 the embryo-sac and the egg-cells, and diagrams must be used. 

 The homologies should be made plain by calling the nucellus 

 macrosporangium and the embryo-sac macrospore, though 

 strictly it is only the very young and ungerminated embryo-sac 

 that is macrospore and the later stage they study is its germi- 

 nated condition. It is not worth while to try to homologize the 

 scales of the cones with carpels ; the homologies are extremely 

 doubtful, in any case, and the most recent studies seem to show 

 that the Gymnosperms are not the ancestral forms of the 

 Angiosperms at all, but have come off from the Pteridophytes 

 by a distinct branch as shown in the table in Fig. 29. It will 

 be well to give the students some idea of the Cycads, and 

 particularly the Cycas with its antherozoids, of which there is 

 a good account in Atkinson's " Elementary Botany." 



VII. The Angiosperms 



a. Monocotyledons 



94. What is the structure and ecology of the forms 

 supplied ? 



