STUDIES AMONG OUR COMMON HEPATICJE. 8i 



the apex and more or less reflexed at the margins. Like the leaves, 

 they are usually entire, but are sometimes slightly toothed near the 

 base. Here again the line of insertion is a sharp curve directed for- 

 ward, and the underleaves are deeply decurrent on both sides. 



The dense crowding together of lobes, lobules and underleaves is 

 of much importance to our plant, which sometimes grows in rather 

 exposed localities. By means of it, nuinerous narrow spaces are 

 formed underneath the broad, protecting lobes, and in these spaces 

 water is readily absorbed and retained, thus preventing the plant from 

 immediately drying up as soon as the supply of water is withheld. In 

 our previous types the stems and leaves have been appressed to the 

 substratum, and have thus been able to retain a certain amount of 

 moisture, but it is clear that our present plant carries out this im- 

 portant function in a more effective way. 



The branches of Porella, sexual as well as vegetative, are all 

 lateral. Each branch starts out just underneath a lobe and takes the 

 place of its lobule, just as in Lepidozia it takes the place of the lower 

 half of a leaf. Here again the first leaf of the branch is an underleaf , 

 but, unlike other underleaves, it is usually slightly connate with the 

 subtending leaf and serves as its lobule. 



Porella platyphylla is dioicous, and the male plants are more 

 slender and more regularly pinnate than the female. The antheridial 

 branches (Fig. 4) usually arise from the primary branches and not 

 from the main stem. They are pale, oblong or oval spikes, each hav- 

 ing about five pairs of delicate, strongly concave and densely crowded 

 bracts. The latter are much less deeply bilobed than the ordinary 

 leaves, and their lobes are more nearly equal in size. The bracteoles 

 are connate with the bracts on both sides. 



The female branch (Fig. 5) sometimes springs from the main 

 stem, but usually from a primary branch." It is very short, and, in 

 addition to the perianth, bears only one pair of bracts, the bracteole 

 between them and the underleaf at the base of the branch. The 

 bracts (Figs. 8, 9) are smaller than the leaves and less deeply compli- 

 cate-bilobed. Their lobes are ovate in shape and acute or obtuse at 

 the apex ; their lobules are smaller and are usually acute ; both lobes 

 and lobules frequently bear small and scattered teeth. The bracteole 

 (Fig. 10) is ovate, free from the leaves, rounded at the apex, and, like 

 the leaves, often sparingly toothed. The most conspicuous feature of 

 the branch is the large perianth (Fig. 5), which is oval in shape and 

 contracted at the mouth. In the upper part it is much flattened dorsi- 

 ventrally, but, toward the base, there is a rounded but distinct keel 

 underneath, which becomes more pronounced as the sporophyte de- 

 velops (Figs. II, 12). The presence of this keel of course indicates 



