234 INTRODUCTION. [part ii. 



ledon, the number of the cotyledons has been 

 chosen as the distinguishing mark of the second 

 great division of plants according to the Natural 

 System. 



The Vascular plants are therefore again 

 divided into the Dicotyledonous plants, which 

 have two or more cotyledons ; and the Mono- 

 cotyledonous plants, which have only one cotyle- 

 don : and to these modern botanists add the 

 Acotyledonous plants, which have no cotyledon, 

 as some of them have spiral vessels, or at least 

 ducts, though most of the Acotyledonous plants 

 belong to the Cellulares. These divisions are not 

 only marked by their cotyledons, but they are so 

 distinct in other respects, that it is sufficient for 

 a botanist to see a leaf, or even a bit of wood 

 without leaves, of any plant, to know at first 

 sight to which of these three divisions the plant 

 belongs. 



If the leaf of a Dicotyledonous plant be 

 examined, it will be found to have a strong 

 vein up the centre, from which other veins 

 proceed on each side (as shown at a 'mjig. 102); 

 and if it be held up to the light, the rest of 

 the leaf will be found to be intersected by 

 numerous smaller veins, so as to appear like 

 network, and hence these leaves are said to be 

 reticulated. The trunk and branches of trees 

 belonging to this division consist, when young, 



