Introduction. 
ix 
oosphere. It is this little oosphere which gives origin to the new fern. After the spermatozoids 
escape, some o'f them pass down the neck of the archegonium, and by their action on the 
oosphere fertilise it, and set up in it the series of changes resulting in the growth of a new 
plant. This new plant is at first, of course, very small, and draws its nourishment from the 
prothallium to which it remains attached, but it is soon evident that it is developing, not 
into a prothallium, but into a fern, like its grandparent. It soon becomes established with 
roots of its own, and the prothallium disappears. 
It will thus be seen that the reproduction of ferns is very different from that of flowering 
plants, though a more or less similar mode is very general in the Cryptogamia. Two 
generations are necessary to complete the cycle of life of the plant, and thus the alternate 
generations are different. It may be as well to mention, however, that occasionally the new 
Prothallium of Adiantum Capillus Veneris, 
seen from below, with the young fern 
attached to it. 
p p. Prothallium X about 30 times ; d. The 
young fern ; id w". Its first and second 
roots ; h. Root-hairs of the Prothallium. 
(After Sachs.) 
I. Prothallium of Aspidium Filix-mas, natural size ; 2. The same, 
much enlarged ; 3. An Antheridium before bursting ; 4. The 
Antherozoid-cells escaping from the Antheridium ; 5. An 
Antherozoid-cell ; 6. An Antherozoid ; 7. An Archegonium : 
all much enlarged. (After Berg and Schmidt.) 
fern arises from the prothallium by a process of budding, without the intervention of repro- 
ductive organs, as was first observed by Dr. Farlow, of Boston, U.S.A. 
Besides the true sexual reproduction above described, ferns, like other plants, are capable 
of increase by means of buds and offsets. Many species constantly viviparous in this way 
are in cultivation ; the buds are either scattered over the fronds or produced in the axils of 
the pinnae. Other species root at the end of the fronds, and so produce there new plants. 
CLASSIFICATION OF FERNS. 
It is not our intention here to exhibit the classification of the whole of the ferns, further 
than to point out the main divisions into which they fall. But it will be convenient to show the 
system upon which the European ferns are most readily arranged, although in the following 
pages this arrangement has not in every case been strictly followed, and to give the botanical 
characters of the different genera to which they respectively belong. 
The above account of the structure of ferns will have shown that there is not a very great 
amount ot difference between the various kinds. We have not, as in flowering plants, organs 
