QUEKETT'S LECTURES ON HISTOLOGY. 



77 



tubercles, c.icli star being attached to the cuticle by its centre. If the 

 cuticle be removed, and boiled in nitric ncid, the stellate hairs may be as 







lf^^t> 



Siliceous cuticle from 

 the under surface of tin- 

 leaf of Dcutzia scabra. 



Portions of woody fibres from 

 the busk of the liice. 



plainly seen as in the natural condition of the leaf; the crenated lines 

 found in all parts of the object representing; the cell-walls of the cuticle. 

 This specimen will serve to show, which it docs in a striking manner, 

 that silica is not confined to the cells of the cuticle, but is equally 

 abundant in the hairs and spines developed upon it." 



The most definite forms assumed by the hard parts of 

 plants, are undoubtedly those found in the DiatomacecB ; but 

 as these have been so copiously illustrated in our pages, we 

 may now pass them over. The Corallines are examples of 

 plants having hard parts, closely resembling those to which 

 we do not deny the name of skeleton in animals. Professor 

 Quekett treats of these in his tenth lecture, with the hard parts 

 of Zoophytes. 



" As the Lithophytes occur in the greatest abundance upon coral reefs, 

 where it would appear that the water is highly charged with carbonate of 

 lime, and, as in former times, they were considered to be Zoophytes, I 

 have thought proper to speak of their minute structure at this time, in 

 order that you may have an opportunity of comparing it with that of the 

 stony axis of the Corallidfe, and I must therefore beg of you to bear in 

 mind that the comparison is of the greatest interest ; for in both instances 

 we have a great abundance of calcareous material which has been sepa- 

 rated from the water by a vital process, that in the one case being effected 

 by a vegetable, the other by an animal basis requiring the presence of 



