124 THE "CLUB-MOSS." 



1. The outermost (epidermal) layer of cells, and the thick 

 cuticle which is the outer layer of its surface walls. 



2. The centrally placed vascular bundle region. Note the 

 distribution of xylem and phloem and compare with the 

 vascular bundle of Pteris. 



3. Draw a sector of the section. 



III. ASEXUAL REPRODUCTION. 



Some sporophylls bear sporangia which contain many small 

 spores; others bear sporangia in which large spores are formed. 

 The two kinds are sometimes found in the same strobilus. 

 Remove and mount several sporophylls, and observe: 



1. The sporangium on each one. Make a drawing of a good 

 specimen. 



2. Open the walls of the sporangium and observe the spores. 



3. Compare the two kinds of sporangia as to color, form, 

 and size, and draw both kinds. 



4. Determine the number of megaspores (large spores) pro- 

 duced in a sporangium. 1 



5. Mount microspores and megaspores so that both can be 

 seen in one view by use of the low power, and make draw- 

 ing showing their relative size and similarity of form. 



IV. SEXUAL REPRODUCTION. 2 



i. The male gametophyte. In a section through the wall of 

 a microspore that has germinated observe; 



1 The number of microspores (small spores) produced in a sporangium 

 is so great that it will not be possible readily to determine their 

 number. 



2 It is very difficult to obtain sections that will show satisfactorily 

 the gametophytes of Selaginella. Directions for making such sections 

 may be found in Chamberlain's "Methods in Plant Histology," pp. nr- 

 113. If sections of the gametophytes of Marsilia can be had, they will 

 serve well in place of those of Selaginella. Usually it will be found much 

 more satisfactory if there are supplied prepared sections of Marsilia or 

 Selaginella for this work. The gametophyte development is not the 

 same in the two genera, but the Selaginella outline can be readily ad- 

 justed to the study of Marsilia. 



