Lecture XVIII. 145 



away the sandy soil and expose the rhizoids ; lay out a few plants on a piece 

 of white paper, or better, opal glass, and examine, with a lens. Make a 

 sketch showing the stem with its branches, the rhizoids and leaves. Also 

 draw a specimen with sporophyte attached. Show the calyptra. 



Mount a few leaves in water, sketch with the low power. Also sketch a 

 small group of cells from the blade of the leaf. Record the shape of the 

 chloroplasts. Observe that they are usually ovoid. Sometimes one is seen 

 constricted in the middle. Instances will be found where the constriction is 

 deep and ultimately leads to fission. The chloroplasts multiply by fission. 

 Application of liquor iodi will bring out minute starch grains in the chloro- 

 plasts. 



Prepare longitudinal sections of the tips of male and female shoots. 

 Make drawings illustrating the form of the antheridia and archegonia* 

 Estimate their size by means of the Ghost-micrometer. Observe the masses 

 of sperm-mother-cells extruded from the antheridia. Careful study of these 

 will show the nuclei and stages in the development of the sperms. 



Make a careful lens drawing of a plant with sporophyte attached. Mark 

 the limits of the gametophyte and sporophyte. Show the calyptra. Remove 

 the calyptra and draw the theca on a larger scale. Show its attachment 

 to the seta ; indicate the apophysis and the operculum. 



With a razor cut a slice off the top of the theca of an immature sporophyte, 

 including the rim of the theca and the operculum. Place it on a dry slide 

 and sketch under the low power. 



Make a similar preparation from a theca which has lost its joperculum. 

 Notice the peristomium, and observe how its teeth bend inwards when you 

 breathe upon it. They curve outwards as they dry. 



Make a longitudinal section of an unripe theca before the operculum is 

 detached. Mount in water and cover. Your preparation should show the 

 columella and sporogenous layer separated by an air space from the wall. 

 Suspending filaments traverse this space and attach the central mass to the 

 wall. Notice the apophysis with air spaces in its outer layers. The oper- 

 culum, the peristomium, the annulus and the rim may be seen in good pre- 

 parations and should be recorded in sketches. 



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