OF THE FERNS AND FLOWERING PLANTS. 157 



which he has already gathered the flower. The same 

 foresight must be extended to the fruit. The latter, indeed, 

 is not indispensable, though certainly desirable ; for the 

 reader may easily picture to himself what confusion and 

 errors may possibly arise, where there is no certainty of 

 the examples, which lie together in the herbarium, having 

 been the produce of the same plant. 



The above remarks refer with tenfold force to the 

 Willows, which seem to have a peculiar facility for hybri- 

 dising ; and, therefore, the greatest care -should be taken 

 to isolate every specimen, and if possible to have it in one's 

 power to identify the very tree from which each was taken. 



The Ferns are no exception to the rule, which demands 

 that the plant should be seen in its integrity when dried. 

 The crown and root must always, if possible, be secured as 

 well as the frond ; and of the latter, those which have no 

 fruit on them must not on that account be passed by, as 

 the two kinds often exhibit wide differences in form, and 

 mark the character of the plant. More than one species of 

 the remarkable genus, Eqnisetum, is furnished with both 

 sterile and fertile fronds ; both of which must of course be 

 •athered and laid side by side in the herbarium. In the 

 case of the common Equisetum arvense, the succulent, 

 fawn-coloured, fruit-bearing stem rises upright from the 

 soil weeks before the harsh green procumbent frond 

 spreads itself over the ground. In others again the fertile 

 shaft is entirely unbranched, while the sterile stems are 

 enriched by frequent whorls of elegant pendant branches. 

 The two sorts of frond may be easily recognised ; while 

 the barren stem tapers gradually to a point, the fertile is 

 furnished with a stout clavate head, which is in fact the 

 receptacle, and contains the spores in a number of separate 

 sporangia. These spores are themselves very interesting 

 objects : each is furnished with four filamentous processes, 

 known as elaters, though very unlike the elaters which are 

 mingled with the spores in the capsules of the Hepatic£3. 

 They are extremely sensitive to the influence of moisture, 



