STAINS AXD STAINING. 293 



two latter are much assisted by hydrochloric acid. The results of 

 these reactions also cannot be preserved in the usual mounting 

 media. 



Sections containing mixed tissue, partly unaltered cellulose 

 and partly lignified, give very striking results with the aniline 

 dyes, with this additional advantage, that the preparations showing 

 the reactions can be preserved for years. 



Double Staining. 



When a section is passed through methyl green solution and 

 afterwards carmine (the minute details I have already published), 

 the lignified portion is coloured green, and the unlignified red. 

 Acid green may be used in the place of methyl green with a like 

 result. When picric acid is used with carmine, nigrosine, or 

 Hoffman's blue, the picric acid dyes the ligneous portion, and the 

 others colour the unlignified structure red, black, and blue 

 respectively. 



Sieve-areas. 



These are well shown by Hoffmann's blue and eosin, also, but 

 not so strikingly, by haematoxylin. Sections representing these 

 combinations will be projected on the screen, and I will bring 

 under your notice the various points as they occur. 



I have now concluded the matter which I wished to put before 

 you, and first I have to thank you for the patient hearing which 

 you have given me, and then to express my gratitude to Mr. Curteis 

 who is handling the lantern, and to my assistant, Mr. Stewart, 

 both of whom have given me great assistance in the preparation 

 of this lecture. 



Insects are the lowest animals known to assist in seed dis- 

 semination. Mr. Darwin tells us of locust excrement containing 

 seeds which grew when planted. Considering that locusts often 

 occur in vast swarms, they can hardly fail to be highly effective 

 agents in seed dissemination, thus repaying to some extent for 

 the immense damage they often do. 



— Popular Science Monthly. 



