Stock ard : Nectar-glands of Vicia Fab a 249 



picro-acetic, and picro-corrosive, all giving good results and sup- 

 plying valuable means of comparison. The same precaution was 

 resorted to with the stains, and from the number tried those best 

 adapted to this material were selected. . 



Auerbach's stain (methyl green and acid fuchsin) was exten- 

 sively used for studying the cell-contents, as it gives a beautiful 

 differentiation of nuclear substances, and differentiates clearly the 

 chromatic granules of the nucleus from the cytoplasmic granules 

 about the nuclear wall. Heidenhain's iron-haematoxylin with 

 congo red as a counter-stain gave far the clearest preparations and 

 is a most valuable stain, although Reed in criticizing Torrey's 

 results, objects on the ground that it does not differentiate between 

 acid and basic elements of the cell. This is an objection in itself 

 open to criticism, as after the use of fixatives we should not depend 

 on any one stain for such differentiation, and probably Auerbach's 

 stain, which Reed failed to use, is best for such purposes. Torrey, 

 himself (page 429), mentions this same objection to an iron- 

 haemotoxylin and states that on this account he resorted to the 

 use of Auerbach's method for comparison. 



Eosin-toluidin blue as recommended by Reed was successfully 

 tried. Eosin and polychrome methylin-blue used separately gave 

 good preparations, while mixed as Romanowsky's stain the results 

 were poor. Throughout this study the artificial conditions of 

 stained preparations were always kept in mind and comparisons 

 continually resorted to so that if errors do exist I believe they 

 should be attributed to other causes. 



OBSERVATIONS ON THE LIVING GLAND 

 The glands are situated on the stipules of the leaves and when 

 mature appear as small dark-red spots, one on each stipule rather 

 near its base.* The immature glands found in the terminal buds 

 are tiny white spots on the pale-green stipules, and the gland is 

 several days old before it becomes colored. They are more con- 

 spicuous on the lower or outer surface of the stipule, being less 

 distinct and velvety in appearance on the upper side, the side, 

 namely, on which the secretion occurs. The velvety appearance 

 is due to the presence of the hairs described below. The secretion 



* First mentioned by Sprengel, Entd. Geheimniss 357. 1793- 



