EUROTIUM 489 



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 

 perithecium, 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 page 12) : first moisten with 

 alcohol, and then wash well with water, and soak thoroughly in 



