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POPULAR SCIENCE REVIEW. 
then exhibit those peculiar movements which 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 cilise, 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. 
Fig. 1. JEcidium grossularice. c. Cluster-cups. s. Spermogones. 
„ 2. Section of ripe spermogones of JEcicliu'in Euphorbice. s. Spermatia. 
a. Sterigmatre bearing spermatia ( De Bary). 
The largest spermatia yet examined (those of Peridermium 
Pirn) have a length equal to ^Vo °f an inch, but their width 
seldom exceeds yooooo 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 appreciable 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 sometimes their presence is only 
indicated by minute depressed punctures which are scarcely 
visible ; generally, however, they may be recognised by an 
