SPERMOGONES. 25 



wWch have been observed in the similar bodies in 

 lichens^ and fitly described as ^^ a sort of oscillating 

 motion^ as of a body attached at one extremity/^ 

 The cause of this motion is at present uncertain, 

 vibratile cilice, to which similar movements are 

 referred, being altogether absent; but probably, 

 as De Bary believes, the cause may be found in 

 the influence of exosmose. 



The largest spermatia yet examined (those of 

 Peridermium Pirn) have a length equal to 25^00 of 

 an inch, but their width seldom exceeds toWo^ of 

 an inch, whilst in others their length does not 

 exceed the width of those just named. 



Messrs. Tulasne affirm that all these corpuscles, 

 as well as the mucilaginous fluid, evolve an appre- 

 ciable odour, resembling that of the pollen of the 

 willow. M. Leveille compares the odour to that of 

 orange flowers, and M. de Bary to that of the 

 evening primrose. 



The spermogones do not always appear like 

 pustules on the surface of the leaves, for some- 

 times their presence is only indicated by minute 

 depressed punctures which are scarcely visible; 

 generally, however, they may be recognized by an 

 obtuse, or otherwise a pointed, protuberance that 

 surmounts them. The margin of the orifice is 

 sometimes furnished with short hairs, but is more 

 frequently ornamented with a pencil of long hairs, 

 which are stiff and erect, and of the colour of the 

 enclosed spermatia. 



