AND CONTENTS OF THE MOUTH. 421 



of their branching filaments, is better seen in the anilines (see in 

 the previous Memoir the Figures lo, 12, 16) ; the solution of iodine 

 would hardly give the same result. This solution has little or no 

 action upon viscid matter ; therefore, the fructifications assume 

 with it a granular aspect, and if the spores are not too thick it 

 shows the peduncles better ; also because the solution of iodine 

 acidulated with lactic acid attacks relatively better the peduncles 

 themselves, whilst the gentian violet invades them less than other 

 elements. Consequently it happens that the solution of iodine 

 better exhibits the complex aspect of the clusters or the truncated 

 sterigmata. (See Fig. 23, d.) It has, however, the disadvantage of 

 not satisfactorily allowing the use of powerful eye-pieces, thus 

 limiting the enlargements ; whilst in the fructifications stained 

 with gentian violet, the details of structure may be (under favour- 

 able conditions) detected even with a No. 6 eye-piece, as is shown 

 in Fig. 24, magnified to 3,100 diameters. 



Now from the concourse of these various circumstances, either 

 relative to the age of the single fructifications, and to the more or 

 less thickening of peduncles and spores, or to the quality and 

 degree of the colouring, we are able to obtain images conspicuous 

 in the whole, but with peduncles only partially or not at all visible, 

 or sometimes less conspicuous in the whole, but with quite dis- 

 tinct peduncles. The necessary conditions to the clear vision of 

 the peduncles in question may be summed up in the following 

 series : — ^, proper optical instruments ; b^ clusters still young ; c, 

 rather thin spores ; d, a weak gentian violet ; or <?, solution of 

 iodine. We have already said that the best images are obtained 

 from isolated fructifications fallen from clods in a clear field, and 

 it is our intention in this work to consider the two colourings above 

 mentioned, apart from the use of other tints. 



The fructifications in question can be observed by axial illu- 

 mination or by oblique light. The best images of the clustered 

 forms and of the single sterigmata are obtained by axial illumina- 

 tion by properly adjusting the correction collar, and by centering 

 the iris diaphragm and the Abbe condenser along the optical axis. 

 On the other hand, the general relief of the ears and the position 

 of the spores in six longitudinal series, are better detected by 

 oblique light, by pushing aside the diaphragm and letting it after- 



