. Foundations of botany. isjuncta. (Enlarged.) /r, female receptacle ; c, cups with gemmae. THE STUDY OFMARCHANTIA 335. Occurrence.— Marchantia grows on soilor rocks in damp shaded places and is widely distributed. 336. The Thallus. —In general form the thallus bears some resem-blance to that of some of the lichens, as Parmelia, but is plainlydifferent in color, mode of branching, and internal structure underthe microscope. Under the microscope (see below) the individualcells may be compared with those of the medullary layer in Physcia. Note the color and general shape of the thallus and study
. Foundations of botany. isjuncta. (Enlarged.) /r, female receptacle ; c, cups with gemmae. THE STUDY OFMARCHANTIA 335. Occurrence.— Marchantia grows on soilor rocks in damp shaded places and is widely distributed. 336. The Thallus. —In general form the thallus bears some resem-blance to that of some of the lichens, as Parmelia, but is plainlydifferent in color, mode of branching, and internal structure underthe microscope. Under the microscope (see below) the individualcells may be compared with those of the medullary layer in Physcia. Note the color and general shape of the thallus and study care-fully the mode of branching. The origin of the growing cells is atthe tip, but cells so originating aftei-ward multiply more rapidly, sothat the tip comes to be in a notch. Viewing the thallus as an opaque object, note the diamond-shapednetwork on the upper surface and the dot-like circle in the middleof each diamond. Examine the under surface for (1) rhizoids and (2) scales. TYPES OF CRYPTOGAMS; BRYOPHYTES 279. Fig. 203. —Section through Anther-idial Receptacle of Marchantia(Magnified.) a, antheridium. 337. Internal Structure. — Cut thin cross-sections of the thallusin the same way as for Physcia, making some pass through the cir-cular dots mentioned above. Exam-ine under a high power and note thedifferent kinds and layers of cellscomposing the thallus. Note thecharacter of the cells forming theupper and lower surfaces. Describethe cells which are next above thoseof the lower epidermis, their shape,color of contents, approximate num-ber of horizontal rows. Have theyany evident intercellular spaces ? Findcells connecting these with the upperepidermis and constituting the net-work of lines seen on the surface of 9 the thallus. Note the air cavitybounded by these lines and the loose cells which occupy it in is the color of their contents ? How are they attached, andhow arranged? Can you discover anyopening through the epidermis? If so,describe it. Make dra
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