198 VEGETABLE ORGANOGRAPHY. 



leaves ; and they can be separated from each other, so 

 that their true nature can be very readily recognised. 

 They form nearly cylindrical tubes, inserted into one 

 another, the transverse section of which is seen when 

 this floral stem is cut horizontally. An analogous 

 organization appears to exist in most of the Scitamineae, 

 although in a less evident manner ; and it is perhaps the 

 same in several other Endogens, when one equally dis- 

 tinguishes a persistent part, (which is the true stem, 

 whatever may be its situation,) and a floral part of 

 limited duration. The distinction between the true 

 stem, and the organs formed by the peduncles and the 

 bases of the leaves, is, in certain genera of this class, 

 very difficult to be fixed with precision. 



§ 4. — The Stem of the Graminese. 



Botanists have usually called the stem of the Gra- 

 minese, or Grasses, by the particular name of the Culm 

 (culmus; chaume); and it deserved in fact a peculiar 

 name in the old system of the nomenclature of organs, 

 where there was a tendency to designate all their modi- 

 fications by proper names : the immense number of 

 these modifications gradually caused this method to be 

 abandoned, because it presented the great inconvenience 

 of conceah'ng under different names the real analogies of 

 organs. 



The Culm differs from other Endogenous stems in 

 this : — that at the origin of each leaf is found a knot or 

 plexus of very numerous and compact fibres ; in every 

 part of the stem between the knots, or in the internodes, 

 the fibres are parallel, vertical, and do not deviate vinder 

 any circumstances ; there are never produced, in this 



