SYSTEM. 229 



rules, and in which nothing like cotyledons can be discovered. 

 Hence the plants of this class are denominated Acotyledonous, 

 that is, without cotyledons. 



VASCULARES, PH.ENOGAMOUS, COTYLEDONOUS, and FLOW- 

 ERING plants are therefore only different terms denoting the 

 same combination of vegetables, and including all the Lin- 

 naean species in which stamens and pistils are found. Also, 

 the terms CELLULARES, CRYPTOGAMOUS, ACOTYLEDONOUS, 

 and FLOWERLESS plants denote the same series of produc- 

 tions, and include such vegetables only as produce neither 

 stamens, pistils, nor flowers. 



In respect to the difference of structure on which these 

 grand divisions are founded, the vasculares all possess 

 spiral internal vessels, a more or less woody fibre, and have 

 their leaves reticulated, the veins not parallel. The term 

 is derived from the Latin vas, a vessel. It is however un- 

 necessary for ordinary purposes, to ascertain the difference 

 between the two classes by dissection, the veins of the 

 leaves and the presence of the stamens and pistils being in 

 all cases sufficient to determine the phaenogamous nature of 

 an individual. 



The term Cellulares is derived from the Latin ccllula, a 

 little cell, and in its application denotes that the plants are 

 cellular, but not vascular in their structure. Cellular plants 

 are formed entirely of cellular tissue, but contain no spiral 

 vessels, nor woody fibre, nor are their leaves traversed by 

 veins, as in the other class. The Ferns, however, approach 

 nearly to the Vasculares, as their fronds possess parts anal- 

 ogous to veins ; but as they are destitute, or nearly so, of 

 spiral vessels, have no parts answering to cotyledons, and are 

 withal entirely flowerless, they are strictly cellular plants. 



These two great, but unequal divisions, being thus estab- 

 lished on anatomical, as well as external characters, the class 

 Vasculares is next separated into two sub-classes, founded 

 on the different laws which govern their growth. It has 

 been ascertained that some of the plants of this class increase 

 by the addition of successive layers of new matter, or wood, 

 on the outside, and that another, but smaller number, grow 

 by additions on the inside. For this reason, the first of these 

 divisions is called Exogenous, and the other Endogenous ; 

 the first term signifying external, and the second internal 

 increase. 



Exogenous plants, of which the Oak may be taken as an 

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