THE VESSELS. 35 



aged trunks of trees, and in wood which has long been 

 cut down. In the fibrous bundles of the herbaceous 

 stems of Dicotyledons, the trachege are found, according 

 to Kieser, in the part nearest the centre of the stem ; 

 among Monocotyledons, they are found in the woody 

 bundles : according to Mirbel, they occupy the cen- 

 tre of them; Amici appropriates this place to the 

 dotted vessels. The stem of the Plantain appears 

 to be almost entirely composed of tracheae, when it is 

 cut across ; they are so abmidant, that in the Antilles 

 they gather them by handsful, and a kind of tinder is 

 made of them, which has long been publicly sold there. 

 M. De la Chesnaye says that each Plantain tree yields 

 five or six grammes (a drachm and a half) of these 

 vessels, and that they may be used either in making a 

 species of fine down, or may even be spun. Tracheae 

 are also found in the veins of leaves, in the corolla and 

 sexual organs, but never in the bark. Mirbel says 

 that they are very rare in the roots. Dutrochet 

 asserts, and my own observations agree with his, that 

 the tracheae are absolutely wanting in the roots; and 

 that those who have fancied they have seen them, must 

 have taken for true roots subterraneous stems which 

 have tracheae just as aerial stems. Perotti must, 

 therefore, be quite wrong when he says that the roots 

 differ from the trunks in having the tracheae more vi- 

 sible and more numerous. Tracheae are entirely wanting 

 in all cellular plants, such as the Mosses, Hepaticae, 

 Lichens, Fungi, Algse, and Chara. 



Some natiuralists, upon whom we may rely, assure us 

 that tracheae exist in some Mosses, as in Splachnum ; 

 but this is doubted by several — as, for instance, by 

 Rudolphi and others. Without denying that a negative 

 observation has not so much weight as a positive 

 assertion, I am of this last opinion, as I have never been 



d2 



