THE PLA^T GROUPS 121 



b. Sporangia and spores. 



(1) Dissect out sporangia into a drop of water on a 



slide. Mount and study the cellular structure of 

 the sporangium carefully. Are the cells all alike 

 in structure and in function? To demonstrate 

 this point remove sporangia to a dry slide. Breathe 

 on them gently and observe quickly under low 

 power. Result? Consult the text discussion of 

 spore dissemination. 



(2) Draw accurate diagrams of a closed and an open 



sporangium as you observe them in your own 

 preparations. Be prepared to explain the peculiar 

 structure and mechanism of the annulus. 



SUPPLEMENTARY STUDIES 



1. Sporogenesis. If slides are available, the essential stages in 

 sporogenesis, or spore forumtion, may be worked out, illustrating 

 the archesporium and tapetum, the sporogenous and spore mother- 

 cell stages, and the formation of tetrads and spores. 



2. Analysis and classification. Each student should learn to 

 use the analytical key and analyze a few species of common ferns. 

 Record your analyses as follows : 



. Family 



b. Genus 



c. Species: scientific name, ; common name, 



GAMETOPHYTE 



After examining growing fern gametophytes, determine and 

 record the following points concerning the habitat and nature 

 of the gamete-bearing plant, or gametophyte generation, of 

 the ferns. : 



1. Habitat. AVhat is the natural habitat of these little plants 

 in nature ? Does, your observation indicate that fern 



