LINK ON THE FLUIDS OF PLANTS. 



105 



scope, I perceived that their vessels (trach&s) alone were tinged 

 with blue, amongst the cells which were not coloured in the 

 slightest degree. It was the entire tube which was equally coloured, 

 though the spiral vessels were differently turned, and more or less 

 evolved. 



In the tubercles of plants, there are vessels (tracMes) which are 

 not united in packets : such vessels in Bigonia discolor, were equally 

 tinged blue with the others. 



A, A, the portions of the vessels of Bigonia discolor uncoloured; B the vessel coloured by the 



precipitate. 



I have repeated these experiments with many plants and always 

 with the same results. There are, however, some very tender plants, 

 such as Impatiens balsamina, Pelargonium, &c. which readily flag 

 when watered with a solution of the cyanuret of potass and iron, 

 consequently, the experiment must not with these be continued too 

 long, for after they begin to flag they will not take up the solution 



Spiral, ringed, and beaded vessels of Plants. 



of the sulphate of iron, and the vessels will not be coloured. I have 

 very frequently observed that all the vessels are not tinged ; that in a 

 the same packet there are blue ones, amongst others which have 

 remained white j and that in general the narrow vessels became 

 more readily coloured than the others. The vessels which are 



