104 WAYSIDE AND WOODLAND FERNS. 



sheaths. The branches have their origin at the base of the 

 sheaths, and are arranged in symmetrical whorls. Like 

 the stem they are jointed, with sheaths, but are solid instead 

 of tubular. Both stem and branches are provided with stomata, 

 or breathing pores, and carry out the functions of ordinary 

 leaves. 



The spore-bearing of the Horsetails differs from the methods 

 adopted both by Ferns and Water-ferns. There are barren 

 stems and fruiting stems just as there are barren and fertile 

 fronds among the Ferns, and in some species of Horsetail there 

 is considerable difference between the two : the specialized fertile 

 stem being deficient in chlorophyll or entirely without it. The 

 fruit is always at the summit of the stem, and takes the form 

 of a kind of cone or catkin, consisting of many series of flat 

 scales each supported by a central stalk, and on its underside 

 are arranged from six to nine capsules containing the spores. 

 These spores are very curious : they are globular in form, and 

 each one is invested with several coats. The outermost coat 

 of the spore splits into four narrow strips which are highly 

 hygroscopic, and these remain attached to the spore at one 

 point only. These elaters, as they are termed, are very sensitive 

 to variations in the humidity of the atmosphere, as may be 

 proved by breathing upon them, however slightly, when they 

 will be seen (through the microscope, of course) to be in active 

 movement. The spores are already provided with chlorophyll, 

 and germination will begin a few hours after they are shed ; 

 but, if they fall on a place unsuitable for development, their 

 possession of chlorophyll will bring about the death of the 

 spore in a few days. The spores of most Ferns if kept dry will 

 retain their vitality for years, and in most cases take months to 

 germinate, even where they have been sown under the most 

 favourable conditions. (Plate 109.) 



The development of the germinating spore into a prothallus, 

 and the production of sexual bodies, as described in the case of 



