CCLTIVATION. 
399 
convenient size ; they should be half filled with good 
drainage material, with the smallest particles at top, 
v T lien another fourth of depth should be occupied by 
fine soil, half sand and peat, one quarter loam, with a 
sprinkling of finely-broken sandstone or soft brick 
slightly pressed down on the top ; it should then be 
■watered and time allowed for the whole to become 
uniformly moist ; then the spores to be very thinly dis- 
tributed over it, the whole covered with a bell-glass 
or a piece of glass same size as pot, to be placed on 
its rim, allowing a space of about one inch between it 
and the surface of the soil. In order to keep the whole 
moderately and constantly moist, the pots should be 
placed in pans of water of half an inch depth, care being' 
taken not to allow the soil to become over saturated; 
and whenever any copious condensation takes place 
on the glass, it should be carefully sponged off. As 
the spores germinate, and the Prothallia become 
crowded, so as to touch each other, they should be im- 
mediately thinned, and if it is desirable to save the 
thinnings they can be removed in little clumps on the 
particles of brick or sandstone to other pots prepared 
as for spores. It is not, however, with all our care in 
sowing different species in separate pots, that the 
species sown come up in the pot in which it was sown : 
plants of it may be found in other pots, or in different 
parts of the house on moist surfaces. This is easily ac- 
counted for, as the least motion of the air carries away 
the spores while in the action of sowing, and indeed 
all superfluity of spores may be with profit distributed 
over the whole house, the moist walls often affording 
abundance of young plants. It also often happens that 
a good crop of Ptcris aguilina is the result, its spores 
