14 Researches respecting the. Organization of Leaves. 



Tlie covjngnte utriculie of gramineous plants represented 

 in the pellicle of maize, fig. 9^ fovm a narrow elongated 

 bodv, instead of being nearly spherical as in other plants. 

 It IS placet! .n the middle of a kind of square area, produced 

 by thcdispositioauf the surroundinoutnculse. The conjugate 

 utri^'ulae are applied to each other Dv their interior faces so 

 exactly, as to make the pore disappear, and to exhibit in its 

 place nothing but a longitudinal line, at the extremities of 

 which IS observed a small circle, v>hich Hedwig considered 

 as an aperture, and which, in my opinion, is formed only 

 bv the juice contained m the utriculje, smce I was able to 

 make the appearance of this circle vanish by slight com- 

 pre3>:ion. Though the form of the conjugate utriculae in the 

 gramineous plant'^ is always such as I liave described, 1 have 

 however reiuarked, both in the leaves which envelop the 

 ear of maize, or in the interior face of the sheath of the 

 leaves, and also in that of the leaves of the sugar-cane, co//- 

 jugate utriculae sufficiently reniform to construct the pore, 

 as seen fig. 11. 1 have even observed some w hich had a 

 perfect resemblance to the conjugate utriculte of other 

 plants, as represented fig. 12. Such a variety in the form 

 of the conjugate utriculae of the same plant is very remark- 

 able. The details I have given, in regard to the structure of 

 pores, seem to prove that these organs are essential to the 

 greater part of vegetables : I however foresee that it may be 

 objected, that they are not indispensably necessary ; since 

 it is said that by blanching a plant may be deprived of its 

 pores. I shall observe in reply, that this assertion is not ve- 

 rified by my observations ; for I have found pores on the 

 blanched leaves of an orchis, which had vegetated below a 

 piece' of blackened pasteboard, on the blanched leaves of let- 

 tuce taken from the heart of the plant, and on the blanched 

 stems of radishes, French beans, and potatoes, which had 

 grown up in a dark cellar. 



It may be objected also, that pores exist only eventually 

 in vegetables, since aquatic plants, which never have any, 

 assume them in those parts which arc exposed to the air, 

 and that plants which have pores lose them by vegetating 

 in water. 



I shall observe in replv, 1st, That if the leaves of the 

 flower of the mesophyllum have pores, while those of the 

 stem are without them, it is a proof that this flower was de- 

 stined to rise above the surface of the water, and not a con- 

 sequence of its vegetation in the air ; that if the pedicle of 

 the water-ranunculus has pores, while its stem is deprived 

 of them, it is because it ought to live in the air, and not 



bc'jause 



