11© Researches respecting thu 



examining these parts, the globules above mentioned, which 

 are found affixed to the utricular membrane, but which can 

 Very readily be detached. 



I do not consider the existence of these pores as certainly 

 proved. In my opinion, these organs still require to be exa- 

 mined by naturalists j and if they find means to prove their 

 existence, a considerable step will be made in the system of 

 Vegetation in regard to the circulation of the juices. 



The leaves at their birth are composed of utriculi so 

 small that they cannot be distinguished even with the help 

 of a microscope ; but in proportion as these leaves grow, 

 the utriculi expand, and are distended by the addition of 

 the juices with which they are penetrated. 



I have several times followed the rapid development of 

 the utriculi in the young leaves of the lily kind of plants, 

 where it is very remarkable ; and I have been astonished in 

 particular, in examining the nenuphar, to see the utriculi 

 of the umbilical cord of the seed, which are scarcely sensi- 

 ble at the time of flowering, develop themselves so much 

 between that period and the time when the seed attains to 

 maturity, that this cord is capable of surrounding it, and even 

 of supplying it with a double covering. It must not, how* 

 ever, be believed that this development of the utriculi is 

 without bounds: nature has nearly fixed its limits; so that 

 after a certain term it sometiines happens, especially in 

 leaves where the vegetation is strong, that the utriculi be- 

 come spontaneously torn, as has been very justly observed 

 by C. Mirbel. 



I examined with great care in some plants of the lily 

 kind the formation of the spontaneous lacerations, and of 

 the vacuities thence arising, to which this author gives the 

 name oi lacuna', and the following is the result of my ob- 

 servations : 



These lacerations are effected in the parenchyme of tire 

 leaves according to the direction of the vessels, so that in a 

 transverse section of the leaf they appear as irregular holes 

 separated from each other by bundles of trache* : in ob- 

 serving these holes with the nncroscope, rags of the torn 

 utricuh are very well distinguished, so that it may be as- 

 serted that in these leaves the Jacunae are only accidental. 



The young leaves of the sc'dla tnfotia have no lacunas 

 when they issue from the bulb : in proportion as they grow 

 up the lacerations are produced ; and when they attain to 

 their natural size the lacunas form longitudinal canals, the 

 ■diameter of which gradually decreases as they approach the 

 bulb, and which at length entirely disappear : in the place 



where 



