BRYOPHYTES— HEPATICAE 275 



first the gametophyte structures under the headings thallus, antheridia, 

 and archegonia, and shall then turn our attention to the sporophyte. 



HEPATICAE 



Some of the liverworts are floating aquatics, but most of them grow 

 on logs or rocks or upon damp ground. They are found at their best in 

 damp, shady places. Many of them may be kept indefinitely in the 

 greenhouse. Riccia, Marchantia, Conocephahis, Preissia, and many 

 others vegetate luxuriously, and often fruit if kept on moist soil in a 

 shady part of the greenhouse, and they do fairly well in the ordinary 

 laboratory if covered with glass and protected from too intense light. 

 Riccia natans is a valuable type for illustrative purposes. It floats 

 freely on the surfaces of ponds and ditches. Early in the spring (during 

 April in the Chicago region) it produces antheridia; then, for a short 

 time (about the first of May), both antheridia and archegonia; and 

 still later, only archegonia. Sporophytes then appear as black dots 

 along the grooves. After the spores are shed, the thallus remains sterile 

 for the rest of the season. Marchantia and similar forms are not diffi- 

 cult to establish out of doors. A rather damp, shady spot close to the 

 north side of a building is best. Scrapings from a board wich has been 

 nearly burned up make the best fertilizer to scatter on the soil, if one 

 is to cultivate Marchantia. Such freezing as Marchantia receives in 

 the vicinity of Chicago does not prevent it from appearing again the 

 next spring. If it is desirable to have material throughout the year, 

 the out-of-door culture may be made in a box which can be brought 

 into the laboratory or greenhouse in the winter. A box 3 feet long, 2 

 feet wide, and 1 foot deep will be convenient. An old window will do. 

 It should have a glass cover. There should be about 6 inches of dirt in 

 the box. A mixture of sand, loam, and charred scrapings will make a 

 good substratum for Marchantia. If one is to raise liverworts in the 

 laboratory, it is absolutely necessary to note carefully the conditions 

 under which they grow in the field. 



Marchantia can be grown very satisfactorily on pots in the green- 

 house. Pots as small as 4 inches in diameter are all right. Have a 

 little black, charred wood mixed with the soil and sow gemmae on the 

 surface. If you take care to sow only gemmae from antheridial plants 

 on one pot and gemmae from archegonial plants on another, you will 

 get only one kind of plant on a pot. If well lighted, the cultures de- 

 velop faster. 



