114 THE BIOLOGY OF A PLANT. 



d. Scrape as before, this time examining the green cells 



(mesophyll) from the upper and the lower parts. 

 Compare them and explain their differences. 



e. Study a bit of epidermis taken from the under side 



where it covers a veiulet. Stain with iodine and 

 aniline chloride, and see if the cells agree chemically 

 with the ordinary epidermal cells from the top or the 

 bottom of the leaflet. 



f. Imbed a bit of a leaflet in celloidin or in pith and 



make cross-sections. (It is difficult to get thin sec- 

 tions of Pteris, but with many hot-house ferns it is 

 easier.) Mount in glycerine and observe 



a. Epidermis. 



ft. Mesophyll. 



y. Stomata. 



d. F'lbro-vascular bundles in the midrib and veinlets. 



e. Prosenchyma, above and below the h'bro-vascular 



bundle of the midrib which it helps to form. 

 C. Indusium and reproductive organs when present 



(Fig. 52). 



?/. Hairs, when present. 



y. Study the venation of a leaflet (Fig. 50) and compare it 

 if possible with that of Osmunda regalis. 



F. Reproduction. 



1. SPORANGIA. 



a. In fertile leaflets dissect off the indusium and study the 



sporangia, the receptacle, etc., with a hand-lens or the 

 naked eye. 



b. Mount sporangia of different ages in water or dilate 



glycerine, and study them first with a low and then 

 with a high power. Observe the capsule, pedicel, 

 annulus, spores (or archesporium), etc., and make 

 sketches. 



2. SPORES. 



Study spores of different ages and observe their contents. 

 Crush a mass of them, stain with iodine, and report your results. 



3. GERMINATION. 



Fill a porous vessel (a flower-pot will answer) with clean 

 fine sand. Set the vessel in a shallow dish of water, and when 



