THE STEM. 31 



(Juncus), and a great variety of herbaceous Dicotyledons, such as the 

 Primrose, &c. Certain widely extending creeping plants afford examples 

 of rhizomes with developed internodes, as the Sand-Sedge (fig. 25), the 

 wire-like rhizome of which extends for many yards under the loose sand, 

 sending up leafy shoots at regular intervals ; the stems of Couch-grass, of 

 various Mints, and other Labiate plants ; as also of certain Ferns, such as 

 Lastrcca Thelypteris, and of the Horsetails (Equisetuni), &c. When the 

 rhizome is erect it has much of the aspect of a root '; and the ordinary 

 form was termed by the old writers a premorse root, the decay of the 

 lower end giving it the appearance of having been gnawed off. Examples 

 of this are not uncommon, as in the Scabiosa succisa in various Umbel- 

 liferge, as Cicuta virosa (fig. 24), where the abbreviated internodes form 

 discoid chambers corresponding with the fistular internodes above, and in 

 the Lady-fern (Aihyrium Fttix-feemina), which consequently rises above 

 ground like a dwarf tree-fern. In Sparganium ramosum we meet with a 

 curious alternation of condensed and elongated internodes, so that the 

 rhizomes appear to consist of a number of corms connected together by 

 branches into an erect candelabrum-like assemblage. 



Fig. 25. 



Saud-Seuge (Carex arcnaria), the creeping fibrous rhizomes rooting at the nodes and 

 sending up flowering stems. 



The true-leaf Region. The leafy stem, or region bearing green 

 foliaceous organs, grows above the soil, either in air or water, ex- 

 posed to the influence of light. Its form and structure are ex- 

 tremely varied, depending chiefly on the mode of development of 

 the internodes, the arrangement of the leaves and mode of deve- 

 lopment of the buds, and the extent to which its existence is pro- 

 longed. The first cause regulates to a great extent the form of 

 the axis, the second the mode of ramification, and the third the 

 size and consistence of the full-grown organ. The principal modi- 

 fications may be most conveniently studied under the heads of ^ 

 1. herbaceous, and 2. ivoody stems. 



