120 STUDY OF COMMON PLANTS. 



The alternation of generations just referred to appears 

 very clearly in the ferns. The oophyte, or sexual gener- 

 ation, includes the stage beginning with the germination 

 of the spore and closing with the fertilization of the 

 oosphere. The sporophyte, or non-sexual generation, be- 

 gins with the formation of the oospore and closes with the 

 mature spore. The prothallium is, therefore, the charac- 

 teristic feature of the oophytic generation, and the leafy 

 plant, in this case the "fern," of the sporophytic generation. 1 



Full instruction for the study of the minute anatomy of 

 ferns is given in a number of accessible manuals, and need 

 not be repeated here. A quite full and satisfactory ac- 

 count of Pteris is given by Sedgwick and Wilson in their 

 General Biology ; Adiantum is well treated by Arthur, 

 Barnes, and Coulter in the Plant Dissection ; and Bower 

 and Vines give sufficient help for a thorough microscopic 

 study of Aspidium. It appears to the writer better, if the 

 time is limited, to undertake complete examination of 

 only one part, preferably the stem, since the leaf repeats 

 in its general structure much of what has already been 

 seen in the flowering plants. In studying the stem, most 

 of the time should be given to the nbro-vascular bundle, 

 including a comparison of its structure with that of the 

 bundle of Indian corn and the apple tree. The investiga- 

 tion may well be extended to various other plants ; but its 

 success will depend on the preparation and judgment of 

 the teacher, and the previous training of the student. On 

 the whole, a comprehensive study of the fibro-vascular 



1 So much depends on a correct conception of the alternation of gen- 

 erations, that the teacher is advised to review, illustrate, and, in short, use 

 all means to make it clear. It stands as a prominent developmental 

 character, common to all the groups of plants from mosses to phanero- 

 gams. Cf. Sachs, History of Botany, pp. 200, 201. 



