82 THE PLANT WORLD. 



that the perianth is of the hypogonianthous type, like that of Lepidozia. 

 The upper part of the perianth is strongly deciirved, so that we can- 

 not see its mouth from above without flattening it out ; its lateral keels 

 likewise are often somewhat deflexed. The inouth itself is surrounded 

 by a circle of fine and short cilia or teeth. 



In the Hepaticae, the study of antheridia and archegonia is beset 

 with many difficulties, and cannot be made complete without the aid 

 of microtome-sections. It is, however, quite easy to dissect out these 

 organs and to learn a little about their appearance and structure. 



The antheridia are developed singly in the axils of their bracts, 

 and there are no paraphyses. Each antheridium (Fig. 7) is borne on 

 a stalk composed of only two rows of cells and is in the fonn of a 

 flattened sphere or disc attached to the stalk by its edge. The wall is 

 made up of thin-walled cells, mostly in a single layer, and the entire 

 cavity is filled with the minute sperm-cells, whose boundaries are quite 

 indistinguishable. When the mature antheridium comes into contact 

 with water, during a shower, for example, it bursts open in the upper 

 part and discharges the sperm -cells, from each of which a male-cell or 

 " spermatozoid " soon escapes and swims about in the water. 



The archegonia (Fig. 13) are developed in clusters and terminate 

 the branches on which they are borne. It is difficult to distinguish 

 these branches until the perianth is formed, but we can usually find 

 good archegonia at the bottom of a young perianth. They are smaller 

 than the antheridia and have the form of slender cylinders rounded 

 at the apex and slightly enlarged toward the base. The enlargement 

 is known as the "venter" of the archegonium, and the upper part as 

 the "neck." Below the venter, the archegoniuiu slightly narrows 

 again into a short stalk composed of several cells The wall of the 

 neck consists of a single layer of cells, arranged in five more or less 

 distinct longitudinal rows, but the wall of the venter is a little thicker 

 and its cells are less regularly arranged. Filling the cavity is a single 

 row of cells with densely granular contents. It is quite impossible to 

 make out directly the limits of these cells, but we can sometimes see 

 a little more distinctlv than the others, and situated at the base of the 

 venter the luost important one of all, namely, the egg-cell or 

 "oosphere." The rest of the cells are called "canal-cells." When 

 the archegonium is mature, the cells at the apex become reddish in 

 color and separate, while the canal-cells break down into a slimy mass, 

 part of which is extruded through the opening. Some of the sperma- 

 tozoids find their way to this opening and swim down the neck toward 

 the oosphere. As soon as one of them has united with this cell, the 

 act of fertilization is complete and the oosphere is changed into a fer- 

 tilized egg-cell or "oospore," which develops into the asexual gener- 



