1 6 FERNS IN THEIR HOMES AND OURS. 



be syringed, as this will destroy their beautiful 

 appearance. 



We now come to consider the fruit, which 

 brings us around to the point from which we 

 started. The spore-cases, as we have seen, vary 

 in size and shape ; but in all instances they arise 

 from the outer layer of cells of the frond upon 

 which they are borne. They hence represent 

 what Sachs calls trichoines (hairs), being developed 

 in the same manner from the external layer of cells 

 as are the hairs on the root, stem, leaves, &c., 

 of plants. If a careful examination be made, with 

 the aid of a pocket lens, of a collection of spore- 

 cases on the back of a frond, there will frequently 

 be found among them some which have not devel- 

 oped, and are still only hairs, sometimes jointed 

 and club-shaped at the end. The condition of the 

 frond on which the fruit is borne being changed 

 from that of the sterile one, it would naturally 

 result that the development of leaf-tissue would be 

 sacrificed to produce the vast quantity of sori 

 which most ferns have ; and accordingly we find 

 that the fertile fronds are usually distinguishable 

 from the sterile ones, as being more contracted. 

 To such an extent is this contraction carried, that 

 we finally see the entire leafy portion disappear, 

 and the fertile frond consist of a mass of spore- 

 cases, connected and held together by the veins 

 of the frond only, as in Osniunda; or by the small- 



