SECT. III. APERTURES. 



periment In the fine pellicle of pulpy fruits, 

 though displaying evidently the most unequivocal 

 traces of organization, no pores have as yet been 

 discovered. But we must not on that account 

 conclude that it is altogether without pores ; or 

 rather, we must conclude that it is still furnished 

 with imperceptible pores. Because it is very well Their ex* 



n -, istence in 



known, that the fruits in question do both absorb f erre d 

 and transpire moisture. But if so, there must of ne- J 

 cessity exist apertures for the passage of the moisture of mois - 

 absorbed or transpired, and by consequence imper- 

 ceptible pores. 



But the diameter of such pores must be extremely 

 minute ; as is obvious from the circumstance of 

 their being altogether invisible even after the ap- 

 plication of the highest magnifying powers. Their 

 extreme minuteness has been also thought to be 

 farther illustrated from the following fact. If an 

 Apple or other pulpy fruit is placed under the re- 

 ceiver of an air pump, and the receiver exhausted, 

 the air contained in the Apple escapes only by the 

 bursting of the epidermis. Hence it has been 

 thought that the pores are so very minute as to be 

 impermeable even to air.* But this conclusion is 

 perhaps rather too hasty. The epidermis of the 

 Apple may be permeable to air, though not in a 

 state of sudden expansion. 



* Mirbel, Phys. Veg. vol. i. p. 80. 



VOL. I. 



