EUROTIUM. 131 



Treat some perithecia with a weak potash solution, 

 mount them in glycerine, and examine under a high 

 power: note 



1. The wall of the perithecium, consisting of a single 

 layer of somewhat flattened cells. 



2. The cavity surrounded by that wall filled with 

 bodies of oval form the asci. 



In order to be able to examine the asci in detail, 

 mount fresh perithecia in glycerine, press with a needle 

 on the cover-slip, so as to burst them, and note 



1. The ruptured wall, as before. 



2. The oval asci, each of which contains eight asco- 

 spores, of oval shape when young, and biconvex-lens 

 shaped when mature. 



3. Other cells may also be found which belong to the 

 filling- tissue or pseudo-parenchyma ; this is derived by 

 ingrowth from the wall of the perithecium, and is only 

 to be found in young perithecia : at the period of 

 maturity it is completely absorbed. 



In order to trace the various steps of development of the peri- 

 thecium, observations should be made at various times during the 

 progress of the culture, and the origin of the asci from the spirally 

 coiled archicarp is to be observed in specimens made transparent 

 with potash and glycerine. Further, the origin of the wall of the 

 perithecium from branch filaments which grow round and invest 

 the archicarp is also to be traced, and finally the ingrowth of the 

 wall between the products of the archicarp, so as to form the 

 " filling-tissue." 



These points, however, and especially those changes which take 

 place in the later stages of development, are best to be seen in 

 sections cut through the perithecium : these may be prepared by 

 carefully embedding in paraffin, or, better, by embedding in 

 white of egg (see Part I. page 5) : first moisten with alcohol, and 



K 2 



