292 VEGETABLE ORGANOGRAPHY. 



present any other differences ; but they usually take the 

 name of Bulbs (bulbi) when they present certain pecu- 

 liarities which deserve to be studied. 



1st. A small number of Dicotyledons, which are 

 called bulbous, have received this term from a double 

 peculiarity of their organization, viz., that their leaves 

 have a petiole flattened at the base, more or less sheath- 

 ing, and their stem is swollen up above the neck into a 

 kind of tubercule ; it results from this, that this tuber- 

 cule, covered by the petiolary sheaths, resembles the 

 bulbs of several Monocotyledons ; such is the structure 

 of Ranunculus bulbosm, Fumaria bulbosa, &c. 



2d. Several Monocotyledons present an analogous 

 disposition, that is to say, they have the leaves sheathing 

 at the base (which is frequent in this class), and at the 

 same time the base of the stem is swollen into a tuber- 

 cule, as in several Irideae, whence results a kind of bulb, 

 which many naturalists call a Bulbo-tuber. 



3d. True bulbs present a very short subterranean 

 stem, reduced almost to a simple plate ; from it the 

 leaves arise in great numbers, overlaying one another, 

 and thus forming an oval or round body ; the external 

 leaves are reduced to the state either of fleshy scales, as 

 in the Lily, and then the bulb is said to be Scaly ; or 

 of short truncated membranous sheaths, as in the 

 Hyacinth, when it is said to be Tun icated. In these last 

 the base of the sheaths, and especially that of the inner 

 ones, is fleshy, as in the scales of the Lily, and approaches 

 them in texture although distinct in form. The inner 

 sheaths have a tendency to elongate into true leaves, 

 and all the radical leaves of the Liliaceee are prolonga- 

 tions of the inner pieces of this bulb. An Onion of the 

 first year is nothing but a terminal bud, situated at the 

 top of an extremely short subterranean stem. 



When this organization is compared with that of a 



