No. 400.] FUNGUS AND ALGA IN LICHENS. 249 
duction (e.g., zoóspore formation), by dividing in certain planes 
instead of in others, etc., to meet the extra demand made upon 
it by the fungus and to form some cells which are affected only 
indirectly, if at all, by the fungus.! 
On these points a few remarks may be made. In the first 
place, those algae which form the gonidia of lichens will grow 
and multiply faster under almost any conditions than the fun- 
gus, and they grow and multiply in lichens less rapidly than 
under favorable conditions outside. In the lichen itself they 
grow and multiply very rapidly at times, much more rapidly 
than the fungus. For example, the gonidia in a fragment of 
Ramalina reticulata, the California lace-lichen, may be made to 
grow and to divide very rapidly by placing the piece in water 
in the comparative warmth of the laboratory in winter. The 
whole lichen does not grow; only the gonidia multiply and 
grow; the fungus grows but little, if at all. Out of doors such 
conditions frequently occur in all lichens. During warm rains 
or fogs, or dews, the gonidia have the advantage; they multiply 
and grow much more rapidly than the fungus; many gonidial 
cells recover what they had lost by too intimate association 
with the fungus. In this way new generations of gonidial cells 
are produced which continue the race in the lichen body and 
thereby prevent the fungus from devouring all at once. In 
other words, though the fungus may be parasitic upon the alga, 
the more vigorous alga is not wholly and at once consumed 
by its parasite, whatever may be the ultimate fate of the gonid- 
ial cells one by one. 
Having seen that the association of fungus and alga in 
lichens is not destructive to all the algal cells at once, it must 
be shown whether the fungus is destructive or injurious to any. 
In all lichens the hyphz and gonidia are in most intimate con- 
tact, the hyphz either closely clasping the gonidial cells or 
filaments, or actually sending one or more haustoria into the 
separate gonidial cells. As a result of such intimate contact, 
Osmotic movement of food and other substances must take 
1 Hedlund, T. Loc. cit. Peirce, G. J. The Nature of the Association of Alga 
and Fungus in Lichens. Proc. Cal. Acad. Sci., Third Series, Botany, vol. i, No. 7, 
1899. | 
