284 ESSENTIALS OF BOTANY 
(b) Fully formed prothallia (Fig. 205) with antheridia, arche- 
gonia, and rhizoids. These may best be seen with l.p. in a prothal- 
lium that has been held by delicate forceps and washed with a gentle 
stream of water from awash-bottle. The prothallium should then be 
mounted, bottom side up, in a concave ground-slide and examined as 
an opaque object and also by transmitted light. 
(c) Prothallia which are developing young fern-plants (Fig. 206). 
In some of these study with h.p. the distribution of the chlorophyll 
yy 
ZU 
Li Na 
Fic. 206. Development of the Sporophyte of a Fern. Vertical section 
through prothallium, 
an, antherozoids; ar, archegonia; c, thickened cushion, in which the foot of 
the young fern-plant is imbedded; rh, rhizoids; /, first leaf; r, root. 
(Magnified.) 
bodies in cells of the prothallus. Draw. Study with l.p. the struc- 
ture and veining of the young fern leaf. Draw. 
Procure some dwarf prothallia that have been growing much 
crowded together and then kept for a day or two with very little 
water. Mount in water, examine with h.p., and look for: 
(d) Antheridia best seen on the margin of the prothallium. Draw. 
(e) Sperms, swimming about in the water. Stain these with 
iodine and draw, showing the body of the sperm and its tuft of 
cilia. 
In prepared slides, if any are attainable, study the structure of an 
archegonium, noting: 
(f) The enlarged ventral portion. 
(g) The elongated neck. Neck canal cells and ventral canal cell. 
(4) The egg within the ventral portion. Draw. 
1 See Bergen and Davis’ Principles of Botany, pp. 316, 317. 
