NUTRITIVE ORGANS OF CELLULAR PLANTS. 307 



their appearance, by bundles of elongated cellules ; and 

 the latter probably are so by imperceptible pores. The 

 entire mass of these plants seems composed of one and 

 the same substance, which takes different forms, and 

 performs various functions, without being able to be 

 divided into distinct organs. It is in this point of view 

 that several authors have thought that we cannot apply 

 to cellular plants the same names which are used for the 

 organs of vascular ones ; thus, for example, Wildenow 

 designated by the name of Cormus every part of these 

 plants which is above ground ; but this term does not 

 appear to me to be correct, since certain cellular plants, 

 as the Truffle, live entirely under ground, and have no 

 organ exactly resembling that which would bear the 

 name of Cormus in the Lycoperdons. Persoon, Acharius, 

 and Lamouroux, less perceived the homogeneity of the 

 nutritive parts of these plants, when they designated by 

 a common and single name every part which did not 

 serve for the reproduction ; Persooa named it Peridium 

 in the Fungi, Acharius Thallus in Lichens, and Lamou- 

 roux Fro7is in the Algse. The first of these terms makes 

 too much allusion to the character of an envelope, which 

 this organ frequently performs; the last signifies too 

 clearly that it is foliaceous, which is not always the case, 

 I am incKned, then, to admit generically the name of 

 Thallus to designate the mass of nutritive organs of 

 cellular plants ; or at least of all the Algae, Fungi, 

 Lichens, and those Hepaticag in which distinct organs 

 cannot be distinguished. 



Most naturalists, neglecting on the contrary this fun- 

 damental idea of the homogeneous nature of the parts 

 of cellular plants, have perpetually described them as 

 composed of parts analogous to those of vascular ones ; 

 but the vagueness of these descriptions is manifested in 

 each sentence, and all those terms ought to be taken 



x2 



