IN VEGETABLE BIOLOGY.- 253 



(c) (R). Eose : xylem and phloem a faint reaction, the colour 

 being far more brown than pink : the other extra-xylemie tissues 

 turn orange or yellow, in which a faint pink can often be 

 detected. 



Isoe/es. Reaction failed with the meristem. 



Fig. Xylem not at all a good reaction, the colour being very 

 brown. The same cjlour is taken by the latex and by the 

 tannin in the cells of the medullary rays. Bast fibres aud 

 collenchyma no reaction. 



Arundo. Endoderrn and xylem brown-pink : the other walls 

 uncoloured. 



Maize. As Arundo. 



(a) (C). Copper sulphate gives a pale grey to xylem and 



hard bast of Rose : a pale lavender (best seen in thickish sec- 



tions) in extra-xylemic tissues. On running in caustic potash 



and boiling, xylem and hard bast become brown (yellow if section 



be thin) ; the other tissues become brown, with a suggestion of 

 greenish. 



Isoetes. Effect of copper sulphate alone is inappreciable. 

 On boiling with caustic potash the meristem walls are turned 

 brown, but the other walls also behave similarly. 



Fig, Before boiling there is a green colour in the xylem, and 

 a very pale grey in the walls of the other tissues : this grey is 

 often not appreciable — it is best seen in the hard bast, in which 

 there is a suggestion of blue. On boiling, the respective colours 

 become more marked. 



From this it might be concluded that the hard bast of the Fig 

 yields a (C) reaction : it must be remembered, however, that no' 

 other proteid reaction — except (X) very faintly — is given by this 

 tissue, while the xylem, which gives proteid reactions, does not 

 do so with copper sulphate and caustic potash. 



Arundo. Walls giving other proteid reactions are turned 

 yellowish grey with copper sulphate : this becomes brown on 

 boiling with caustic potash. 



Maize. Much as Arundo. 



(e) Gnezda's test. Rose : xylem and hard bast a pale brown- 

 yellow, seen well only when the section is somewhat thick : 

 collenchyma, soft bast, and cambium a dirty pink. No change 

 of colour on adding caustic potash. 



Isoetes. Meristem walls a pale brown. 



Fig. Xylem yellow: other tissues pale yellow, best seen in 



