230 
METHODS IN PLANT HISTOLOGY 
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. Sporo- 
phytes 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 difficult to establish out of 
doors. A rather damp, shady spot close to the north side of a building 
is best. Scrapings from a board which 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 labora¬ 
tory or greenhouse in the winter. A box 3 feet long, 2 feet wide, 
and 1 foot deep will be convenient. It should have a glass cover; 
an old window will do. 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 condi¬ 
tions under which they grow in the field. 
The living plants are very desirable, since they not only furnish 
the best possible material for habit work and the coarser microscopic 
study, but they also enable one to secure complete series in the 
development of the various organs. 
If even a small room in a greenhouse is available, liverworts can 
be grown in great variety and abundance. On one side of the room, 
have a pile of rocks. Half of this space should be occupied by lime¬ 
stone rocks, held in place with as little mortar as possible. There 
should be some shale and some porous red brick. The whole should 
be arranged so that water may trickle down from above. A pipe 
with holes xV inch in diameter will furnish enough water. The other 
three sides may be built up of various rocks, and some clay, so as to 
form a table about 1 m. high. A small fountain, with a bowl a 
couple of feet in diameter, built of rocks, will add to the efficiency. 
If a few well-supported cement tanks be placed above the principal 
pile of rocks, Isoetes and all the water ferns may be grown there, 
besides Elodea, Myriophyllum, Chara, and other forms constantly 
needed in laboratory work. 
