STUDIES AMONG OUR COMMON HEPATICyE. loi 



bounded on the outside by somewhat thicker walls and a transverse 

 section of a leaf will show that these thickened walls are continued 

 over the two free surfaces of all the cells. 



In addition to the two rows of well-developed leaves, there may 

 sometimes be found a third row of minute, rudimentary leaves. They 

 are situated on the lower surface of the stem, and, from their posi- 

 tion are properly known as "underleaves." They Should be sought 

 for among the crowded rootlets, and. as they are inconspicuous from 

 their pale color and are also transitory structures, they are rarely to be 

 found except near the apex of the stem. There is typically one of 

 these underleaves developed for each pair of normal leaves ; they are 

 very variable in shape and are deeply divided into two slender, ciliated 

 or toothed segments. 



Jiingerjnannia barbata is a " dioicous " species, that is, the anthe- 

 ridia and the archegonia are borne on different plants. In connection 

 with these organs we shall find that the leaves become peculiarly 

 modified, giving rise to what are termed " bracts." Those developed 

 in connection with the antheridia are known as " perigonial " bracts, 

 and those in connection with the archegonia, as " perichaetial " bracts. 



The plants which bear the antheridia are somewhat slenderer than 

 sterile plants, particularly in the parts where the antheridia with their 

 bracts are found. These latter are borne in clusters of five to ten 

 pairs; they do not terminate the growth of the stem, but may be suc- 

 ceeded by ordinary leaves. When dissected off and spread out, the 

 bracts are very like normal leaves, although they occasionally bear one 

 or two slender teeth on the upper margin close to the base. While still 

 attached to the stein, however, they present a very different appear- 

 ance ; they are attached by a line of insertion which becomes almost 

 transverse above and the}^ are at the same time strongly concave, so that 

 each bract encloses a little pouch between itself and the stem Within 

 this pouch (but attached to the stem), the antheridia are developed 

 in clusters of from two to five ; mixed with them, are frequently found 

 minute pointed, leaf -like " paraphyses," which vary greatly in shape 

 and which apparently aid the bracts in retaining moisture for the an- 

 theridia and in thus preventing their shriveling away. The under- 

 leaves corresponding to the bracts are similar to those found on sterile 

 stems. 



Unlike the antheridia, the archegonia are borne in terminal clus- 

 ters and stop the further elongation of the stem which bears them. After 

 they have been formed, and particularly if fertilization has taken place 

 in one of them, there is developed from just below a peculiar, hollow, 

 cylindrical organ, known as the " perianth." This extends far beyond 

 the archegonia, becomes contracted and plicate in the upper part, and, 



