Introductory View of the Natiiml Sptem of Plants. 33 



are formed entirely of cellular tissue {Jig. 9.)) without woody 

 fibre or spiral vessels; or, in more familiar terms, by their 

 having no veins in their leaves if foliaceous, and not forming 

 wood ; they are also destitute of perfect flowers. The lower 

 tribes, such as i^iingi and ^'lga3,°are destitute of leaves, and in 

 some points approach the animal kingdom so nearly as to be 

 scarcely distinguishable from it. In the highest tribe, jFllices, 

 apparent veins are formed in the leaves ; but, as they are imper- 

 fectly supplied with spiral vessels, they cannot be considered 

 more than analogous to the veins of other plants. Ferns, how- 

 ever, hold the intermediate station between Cellulares and 

 Vasculares, and are chiefly retained among the former, on 

 account of their perfect accordance in other respects. In 

 the whole of Acotyledones it is unnecessary to examine the 

 seed for the purpose of determining whether it has one co- 

 tyledon, several cotyledons, or none, the structure of the 

 perfect plant giving the most obvious and satisfactory evi- 

 dence. 



Vascula^res, Phanerogamous, or Cotyledonous plants 

 are also separated into two great classes, called Endogenes or 

 Monocotyledones, and Exogenes or Dicotyledones, both 

 which are distinguished as accurately by their obvious physi- 

 cal structure as they are by the minute and obscure peculiari- 

 ties of the seed. They are all formed with cellular tissue, 

 woody fibre, and spiral vessels {Jig. 10.), and their leaves are 

 traversed by veins ; the last character is sufficient for practical 

 purposes, if it is remembered that they also bear perfect 

 flowers, (that is, flowers furnished either with stamina or pis- 

 tilla, or both,) which always prevent their being confounded 

 with the highest tribes of Cellulares. 



/, Vertical section of a vascular stem. 

 m. Woody fibre. 

 1^ «, Spiral vessel. 



Vol. I.— No. 1, 



o. Leaf of a dicotyledonous plant, 



Py Leaf of a monocotyledonous plant ^ 



