384 APPENDIX. 



11. The leaflets. Note (a) shape, as to outline and margin, 

 comparing basal, median, and terminal leaflets of any branch ; 

 (b) the veins, containing branches of the stele ; (c) the green tissues 

 between the veins. (^[ 154.) 



12. Demonstration. Strip off a bit of epidermis, mount and show 

 (a) the irregular form of epidermal cells; (b) the intercellular 

 openings with guard cells (stomata). (^[T[ 165, 166.) 



13. Demonstration. Cut a very thin vertical section of a leaf 

 at right angles to veins, and show (a) the upper and lower layer 

 of cells forming the epidermis; (b) the green parenchyma cells with 

 intercellular spaces; (r) the section of the vein composed of the 

 stele with mechanical tissues above and below it. (1I^[ 167, 168.) 



14. At the edges of the leaflets on the under side crescentic 

 brown spots, sort. (^[ 323.) 



15. Boil a leaflet for a minute in water. With a needle turn 

 back a flap which covers the sorus, the indusium; observe that 

 it is a specialized portion of the edge of leaflet. 



16. On the under side of the indusium, a mass of yellowish 

 spheroidal bodies, the sporangia. Scrape away most of them and 

 notice the relation of their points of attachment to the veins. 



Mount some of the sporangia and observe 



17. Their shape; the stalk by which they were attached. (Fig. 

 401.) 



18. The darker ridge, annulus, which serves to burst them 

 when mature. (Fig. 401.) 



19. Study the manner of bursting. Tear a bit of indusium from 

 a dried specimen previously soaked in water, removing most of 

 the sporangia. Allow it to dry while watching it with a lens, 

 illuminating from above. 



20. Demonstration. Mount sporangia and spores and show 

 their structure, especially the annulus. 



B. HORSETAIL (Eqins'tum arvense}. 



I. The gametophyte cannot be readily obtained, and differs 

 from that of the fern mainly in having erect branches, with the 

 sex organs on the upper side and always on separate plants.* 



II. The sporophyte. Taking the underground parts in water, 

 observe 



* See Goebel, Outlines of Classification, figs. 210, 211; Campbell, Mosses and Ferns, 

 fig. 220 ; Sachs, Physiology of Plants, figs. 425, 426. 



