284 ESSENTIALS OF BOTANY 



(5) 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 a wash-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 



Fig. 206. Development of the Sporophyte of a Tern. Vertical section 

 through prothallium. 



an, antherozoids ; ar, archegonia; c, tliickeued cushion, in which the ioot of 

 the young fern-plant is imbedded; r/i, rhizoids; I, 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 an'd its tuft of 

 cilia. 



In prepared slides, if any are attainable, study the structure of an 

 archegonium, noting : 



(/) The enlarged ventral portion. 



(j)) The elongated neck. Neck canal cells and ventral canal cell. 



(A) The egg within the ventral portion.^ Draw. 



1 See Bergen and Davis' Principles of Botany, pp. 316, .317. 



