=47. Marchantia.=—One of the larger and coarser liverworts is figured at 31. This is a very common liverwort, growing in very damp and muddy places and also along the margins of streams, on the mud or upon the surfaces of rocks which are bathed with the water. This is known as _Marchantia polymorpha_. If we examine the under surface of the marchantia we see numerous hair-like processes which attach the plant to the soil. Under the microscope we see that some of these are similar to the root hairs of the seedlings which we have been studying, and they serve the purpose of absorption. Since, however, there are no roots on the marchantia plant, these hair-like outgrowths are usually termed here _rhizoids_. In marchantia they are of two kinds, one kind the simple ones with smooth walls, and the other kind in which the inner surfaces of the walls are roughened by processes which extend inward in the form of irregular tooth-like points. Besides the hairs on the under side of the thallus we note especially near the growing end that there are two rows of leaf-like scales, those at the end of the thallus curving up over the growing end, thus serving to protect the delicate tissues at the growing point. [Illustration: Fig. 31. Marchantia plant with cupules and gemmæ; rhizoids below.] [Illustration: Fig. 32. Portion of plant of Frullania, a foliose liverwort.] [Illustration: Fig. 33. Portion of same more highly magnified, showing overlapping leaves.] [Illustration: Fig. 34. Under side, showing forked under row of leaves and lobes of lateral leaves.] =48. Frullania.=—In fig. 32 is shown another liverwort, which differs greatly in form from the ones we have just been studying in that there is a well-defined axis with lateral leaf-like outgrowths. Such liverworts are called foliose liverworts. Besides these two quite prominent rows of leaves there is a third row of poorly developed leaves on the under surface. Also from the under surface of the axis we see here and there slender outgrowths, the rhizoids, through which much of the water is absorbed. [Illustration: Fig. 35. Foliose liverwort (bazzania) showing dichotomous branching and overlapping leaves.] =49. Absorption by the mosses.=—Among the mosses, which are usually common in moist and shaded situations, examples are abundant which are suitable for the study of the organs of absorption. If we take for example a plant of mnium (M. affine), which is illustrated in fig. 36, we note that it consists of a slender axis with thin flat, green, leaf-like expansions, Examining with the microscope the lower end of the axis, which is attached to the substratum, there are seen numerous brown-colored threads more or less branched. [Illustration: Fig. 36. Female plant (gametophyte) of a moss (mnium), showing rhizoids below, and the tuft of leaves above, which protect the archegonia.]