18 FERNS OF KENTUCKY. 
FERTILIZATION 
The subject of the fertilization of ferns is as interesting 
as it is difficult of comprehension. In a book of this kind, 
intended for popular use, it will be impossible to go into all 
the details of the subject. I will, therefore, only give an 
outline of the process of fertilization, as it is at present un- 
derstood by the best authorities. In his “Text-book of 
Botany,” Prof. Sachs has given a very elaborate account 
of the fertilization of ferns, with illustrations, a few of 
which I have copied. 
The first question to be discussed relates to the form and 
nature of the fertilizing organs. As I have already said, 
they are generally situated upon the back of the leaf or 
frond. With the aid of a pocket lens any one can see their 
exact position, whether on the margin of the leaf or at its 
center; whether they form round, horse shoe-like, or elon- 
gated patches. All these distinctions are very important in 
classification; and, when their significance 1s once under- 
stood, the student will be able to classify the individual 
members of any genus, native or exotic. It is, however, 
impossible to determine the form of the organs of fertil- 
ization without the aid of a microscope; but it need not be 
of very high power. 
The term sorus (a heap) is used in describing a single 
patch; the plural, sov7, in describing a number of these 
patches. When the fertile frond is observed under the 
microscope, the sorus is found to be composed of a num- 
ber of beautiful objects, ornamented with something like a 
