18 MICROSCOPIC FDXGI. 



resemble the pappus crowning the fruits of some 

 composite plants than tlie cups of ^cidium. The 

 peridia are very long, and split down throughout 

 their length into threadlike filaments of attached 

 cells ; these gradually fall away and break up into 

 their component parts till but short portions 

 remain attached to the base of the peridia. These 

 cells are elongated and marked on the surface with 

 waved lines, forming in themselves pretty objects for 

 a high power of the microscope (plate II. figs. 23, 24). 

 If the teeth of ^cidium resemble the peristome of 

 some mosses, such as Sjplachnumj the threads of 

 this sipecies of Rcestelia, except in not being twisted, 

 somewhat resemble the peristomes of other mosses 

 of the genus Tortula. The spores in this species 

 are less conspicuous, being of a light brown, and 

 the whole plant, from its modest hue, may be 

 readily passed over without attracting attention 

 unless occurring in abundance. 



The leaves of pear-trees afibrd a second species 

 of this genus sufficiently distinct to commend it to 

 our notice. Sometimes it is very common, at others 

 but few examples are to be met with. The clusters 

 occur on the under- surface, and consist of half-a- 

 dozen or less of large peridia, pointed at the apex 

 and swelling in the middle so as to become urn- 

 shaped (plate II. figs. 20, 21). These vessels or 

 thec£e split into numerous threads or lachiias, which 

 remain united together at the apex. Like the 

 species abeady noticed^ this is brown and incon- 



