CHAP. ir. 



STEM. 61 



Besides the bulbs properly so called, there are certain 

 leaf-buds, developed upon stems in the air, and separating 

 spontaneously from the part that bears them, which are alto- 

 gether of the nature of bulbs. Such are found in Lilium 

 tigrinum, some Alliums, &c. They have been called bulhilli, 

 propagines, sautilles, bacilli, &;c. Care must be taken not to 

 follow some botanists, in confounding with them the seeds of 

 certain Amaryllideae, which have a fleshy coat; but which, 

 with a vague external resemblance to bulbs, have in every re- 

 spect the structure of genuine seeds. 



The tegmenta^ or scales of the bud, have received the fol- 

 lowing names, according to the part of the leaf of which they 

 appear to be a transformation ; such terms are, however, but 

 seldom employed : — 



1. Foliacea, when they are abortive leaves, as in Daphne 

 Mezereum. 



2. Petiolacea, when they are formed by the persistent base 

 of the petiole, as in Juglans regia. 



3. Stipulacea, when they arise from the union of stipules, 

 which roll together and envelope the young shoot, as in Car- 

 pinus, Ostrya, Magnolia, &c. 



4. Fulcracea, when they are formed of petioles and stipules 

 combined, as in Prunus domestica, &c. — {Rich. Nouv. Elem. 

 134. ed. 3.) 



The m.anner in which the young leaves are arranged within 

 the leaf-bud is cdWeA foliation, or vernation. The names applied 

 to the various modifications of this will be explained in 

 Glossolog}^ ; they are of great practical importance both for 

 distinguishing species, genera, and even natural orders ; 

 but have, nevertheless, received very little general atten- 

 tion. The vernation of Prunus Cerasus is conduplicate ; of 

 Prunus domestica, convolute; of Filices and Cycadeae, circinate, 

 and so on. 



2. Of its External Modifications. 



It has already been stated, that the first direction taken by 

 the stem immediately upon its developement is upwards into 



