354 MALE FERN. 



obtained from eacli prothallus cut. Note especially the 

 archegonia, and try to make out the axial series of cells 

 the elongated neck canal-cell (sometimes divided into 

 two), the small rounded ventral canal-cell below this, and 

 the large rounded egg-cell embedded in the cushion tissue ; 

 the neck, consisting of a single layer of cells. In the 

 antheridia, note the single-layered wall and the central 

 mass of antherozoid mother-cells. 



498. Young Sporophyte. With lens, or low power of 

 microscope, examine prothalli with young Fern-plant 

 attached. Note that the young plant grows out from the 



Fig. 88. FERN. Part of a Longitudinal Section of a Prothallus, showing 

 Antheridia. 



underside of the prothallus, near the notched anterior end, 

 and consists of the following parts: (1) the first root, 

 which grows down into the soil ; (2) the first leaf (coty- 

 ledon), which turns upwards through the notch of the 

 prothallus and consists of a relatively long stalk and a 

 simple or lobed blade ; (3) the foot, a projecting body 

 buried in the tissue of the prothallus ; (4) the growing tip 

 of the young stem, lying in the angle between the base of 

 the cotyledon and the foot and showing several developing 

 leaves. In very young plants, note that the primary root 

 is usually the first part to break out through the sheath 

 (calyptra) formed by the prothallus tissue surrounding 

 the embryo. 



In older plants, note (1) the additional roots that grow 

 out from the stem ; (2) the later leaves, which are succeS' 



