TISSUE OF FIBRES. 69 



Hooke says there is much more difficulty in dis- 

 covering the true nature of such minute objects with 

 the microscope, than with the naked eye, and in dis- 

 tinguishing between a perforation and a transparent 

 point. 



Kieser thinks that under a very highly magnifying 

 power, he has in some vessels detected the existence 

 of pores. 



M. De Candolle suggests the probability of these 

 supposed pores being small glands, destined in some 

 way to contribute to the nutrition of the plant. 



M. Mirbel describes them as similar to the pores in 

 the outer bark, being furnished at their orifices with a 

 bulging border. 



M. Amici agrees with this observation, and hence 

 concludes, that the pores are not for the transmission 

 of fluids, but of gases, evolved in the interior of the 

 plant. 



M. Dutrochet again denies the existence of the pores, 

 which he says are globular cells, filled with green 

 transparent matter, the supposed hole in the centre 

 being an optical deception. He ascertained that, by 

 boiling the parts supposed to contain pores, in hot 

 nitric acid, they were rendered opaque; and again, 

 upon neutralising the imbibed acid with caustic potass, 

 their transparency was restored a change incompatible 

 with perforation. 



M. A. Richard, on the other hand, thinks Dutrochet 

 is entirely mistaken, and that, having overlooked the 

 real pores, he has described what M. Turpin has 

 recently termed globuline. 



