114 Elementary Biology. 



organs are developed, and from the female organ after it 

 has been fertilised the new fern springs. 



Following the course we adopted in the description of 

 the moss, we ought to begin our study of the life-history of 

 the fern by an account of the thallus ; it will be more con- 

 venient, however, to commence with the product of sexual 

 reproduction, i.e. the fern so called. As already stated, we 

 distinguish in the adult fern, rhizome, roots, shoots, and 

 fronds. It will be necessary to describe these successively 

 in detail. 



Rhizome. The rhizome of Pteris aquilina consists of 

 an elongated, brown, scaly body, irregularly thickened at 

 intervals where the fronds are given off. To these thickened 

 portions the term node is given, whilst the space between 

 any two nodes is naturally termed an internode. The 

 rhizome itself is covered by a scaly integument, dark 

 brown in colour save along either side, where there is a 

 lighter strip termed the lateral line. The rhizome shows 

 as a whole a difference in age from one end to the other. 

 One extremity is pointed the growing point whilst the 

 other end is thicker, darker, and apparently withering away. 

 The nodes also give rise to shoots which are successively 

 older from the pointed to the withered end of the rhizome. 

 It is worthy of note that the growing point is not bud-like 

 whilst the shoots are so. It is the second youngest shoot 

 that shows fronds above ground, the older shoots having 

 done so in past seasons, and the youngest shoot being 

 that which will take the place of the present bunch of 

 fronds in the following year. Over the outside of the 

 rhizome the leaf-scales, ramenta, or paleae have already 

 been alluded to. They must not be mistaken for the true 

 leaves whose origin they surround. 



The minute structure of the rhizome is of considerable 

 importance, as in it we come face to face for the first time 

 with that great differentiation of tissues so characteristic of 

 the higher plants. If a transverse section be microscopically 



