OYganlzation of Leaves. 115 



cuius to another, when we are not acquainted with the aper- 

 tures proper for affording them a passage ? It cannot, how- 

 ever, be doubted that the utricuU receive, by some way or 

 other, the juice destined for them, since they are full of it, 

 since they repair the daily loss of it which they sustain by 

 evaporation, and since they are susceptible of great deve- 

 lopment. But what is the method employed by nature for 

 this purpose ? I confess that I do not know, having never 

 been able to discover it, notwithstanding the perseverance of 

 my researches. 



C. Mirbel, having observed that the membranes of his 

 cellular tissue were perforated with pores, established by 

 their means the communication of the cells between each 

 other, and the slow transfusion of the juice into that tissue. 



A discovery of so much importance was worthy of attract- 

 ing my notice ; I therefore paid particular attention to it. 

 I first examined the utriculi of the sugar-cane, and I in- 

 deed found that their membrane seemed to be perforated 

 with a creat number of small pores ; but, decreasing or 

 shading 'the light by placing my hand before the reflecting 

 mirror, these pores appeared to me to be nothing else than 

 elevated, whitish, and opake points, which reflected the 

 light ; and this doubtless would not have been the case had 

 they been apertures. 



I examined these pores in the stems of the asparagus and 

 the horse-tail, in consequence of what had been announced 

 by C. Mirbel ; but they are much less sensible in these 

 plants than in the sugar-cane. I perceived them very di- 

 stinctly in the utriculi of the stem of the white poppy, 

 fig. 20^ and in those of the pith of the elder, where they are 

 large, elongated, and disposed in the direction of the breadth 

 of the stem. Though these points, on the first view, have 

 the appearance of apertures, there is reason to believe that 

 they are only prominent semi-transparent points, since I 

 have seen the shadow of them change its place according as 

 I varied the light by moving the reflecting mirror. 



These jioints appeared to me to form part of, and to be- 

 long to, the utricular membrane ; for I could not detach 

 them without tearing that membrane. 



Though my opinion in regard to these pores be difTercnt 

 from that of C. Mirbel, I- do not pretend to give it as cer- 

 tain ; for I must confess that the inspection of objects so 

 small may be accompanied with some optical illusion. I 

 shall howcvt-r add, that I could not discover these pores 

 in the utriculi of the parcnchyme of the leaves ; and I nmst 

 reu:ark, as a cause of error very easy to be conunitted in 

 11 2 ' exaunuiiig; 



