74 
NOTES ON COLLECTING FEENS. 
Owing to the great similarity in the appearance of the 
prothallia of most common ferns, it is often difficult to tell 
to what species they belong. It is best to first select 
specimens with the little ferns attached to them, so that 
one can tell the species, and then examine others of the 
same group for the earlier stages. 
For future study the prothallia may be preserved in 
ordinary alcohol, or alcohol to which 10 per cent, of 
strong acetic acid has been added. 
Of course, the surest way to get the prothallia of a given 
species of fern is to grow them from the spores, and this 
plan may be recommended to those who are willing to 
take a little trouble. The fresh spores may be sown 
either upon fine earth, rotten wood, or bits of tile. These 
must be kept moist, but not as a rule soaking wet. It is 
advisable to sterilize the earth by heating. The bits of 
tile or rotten wood may be plunged into boiling water for 
an hour or so before the spores are sown. This checks the 
development of mosses and algse, which otherwise are apt 
to choke out the young ferns. It is also advisable to 
remove from time to time such alien growths as may 
appear, in spite of the sterilizing of the soil. 
A microscopic study of the prothallium shows that it 
bears reproductive organs within which are produced 
sexual cells—actively swimming sperms or male cells— 
and non-motile eggs, female cells, both sperms and eggs 
much resembling the corresponding reproductive cells of 
an animal. As in the latter there is a fusion of the two 
sex cells, the fertilized egg then developing into the future 
fern. This embryo plant soon shows the characteristic 
leaf, and a root is formed which grows downward into the 
earth. The young fern, however, retains its connection 
with the prothallium for some time, but ultimately the 
prothallium dies, leaving the little fern or “ sporophyte ” 
rooted in the ground. 
The sporophyte, or fern as we usually know it, is a 
strictly non-sexual organism, as the reproductive cells or 
spores are produced by simple cell division, and there is 
nothing in the nature of fertilization preliminary to their 
germination. 
It is thus evident that in the fern there is an alternate 
development of sexual plants ( 'prothallia ) derived from 
the germination of the spores, and of non-sexual plants 
(sporophytes) arising from the fertilized egg. 
There is every reason to believe that the sexual plant or 
