ORGANIC EVOLUTION 141 



Study the spores, and, if material be at hand, their 

 germination also. 



Study the prothallia: their form, their parts, their arche- 

 gonia and antheridia. 



Study the young sporophyte, both before and after the 

 acquisition of independent foraging organs. If a few pre- 

 pared sections of its earlier stages of development are at 

 hand they will be especially instructive. 



The record of this study may well consist in a brief 

 account of the life history of the fern, with drawings and 

 diagrams to illustrate it. 



Study ig. The general structure of the fern sporophyte. 



Materials needed: A growing fern plant; fresh or 

 alcoholic rhizomes of Pteris, and also macerated specimens 

 of same for use in tracing vessels; prepared slides of leaf 

 and root tips ; mounted sections and dissociation prepara- 

 tions of vascular bundle elements. 



Study the distribution of the vascular system. 



Study the leaf: The epidermis in a freshly stripped piece, 

 mounted in alcohol; the air spaces, internal tissues and 

 distribution of vessels in cross sections. 



Study the root tips, the arrangement of rhizoids, the loca- 

 tion of root cap and vascular bundles. 



Study the vascular bundle structure, sufficiently at least 

 to locate and identify the principal supporting and conduc- 

 ting- tissue elements. 



The record of this study may consist in notes and draw- 

 ings of things observed. 



Study 20. A comparison of developmental features of 



other pteridophytes. 



Materials needed: Fresh stems of the scouring rush 

 (Equisetum hyemale) ; fresh fruiting cones of the common 

 horsetail (E. arvense) these may be had in line condition if 



