HOFFMANN ON THE CIRCULATION 



results are met with, and it is especially seen here, that the 

 function ordinarily attributed to the system of the spiral vessels 

 and their allies, is devoid of all proof in fact, and has been de- 

 duced from experiments in which sufficient regard was not paid 

 to all the circumstances involved. At the conclusion of the 

 third part of this essay, relating to the Dicotyledons, I shall 

 examine these experiments more closely, and seek to demon- 

 strate the causes which have so long restricted us to conjectures 

 and opinions, in a matter which appears so simple. 



Since in the plants now to be considered, new organs } flowers, 

 organs of fructification, and ovules, are added to those already 

 examined ; since, moreover, a far greater variety becomes evident 

 in the forms of the internal structure, and the physiological rela- 

 tions of the roots, stem, leaves, &c., of the Monocotyledons, 

 than exists in the majority of the Acotyledons ; the observation 

 of the progress of the sap within these different structures, pos- 

 sessing peculiar forms in the diverse families, acquires greater 

 importance, and admits of conclusions of a far more compre- 

 hensive nature. I therefore take permission to enter more 

 minutely into the details, in order to introduce the more extended 

 remarks in fitting places. 



The experiments, as in the above-mentioned cases, w r ere made, 

 with the exception of Canna, on pot plants alone, which were 

 treated in the ordinary manner. In order to discover the course 

 of the sap, the earth was watered with a solution (always of 

 pretty equal concentration) of ferrocyanide of potassium, and 

 then, after this fluid had been absorbed by the uninjured roots, 

 the parts where absorption had occurred were demonstrated in 

 transverse and longitudinal sections of the plants^ by means of 

 sulphate of peroxide of iron. 



Anomatheca cruenta, Lindl. (Iridaceae). Watered on the 16th 

 of July ; in two hours the ferrocyanide of potassium could be 

 detected in the bulbs, while it was sought in vain in the stems. 

 In the petals also (even in those developed subsequently to the 

 watering and investigated three weeks after), the sap could not 

 be traced, although at first appearance it seemed to have entered 

 them, since they contain a red colouring matter which is readily 

 decomposed and changed into a blue colour; but a counter- 

 experiment with pure water, with a careful application of the 



