6o THE STORY OF PLANT LIFE 



In Monocotyledons there is but one cotyledon, 

 and this is lateral or sheathes the plumule in 

 Graminese. Ray first differentiated these two groups, 

 which are distinguished further by other characters 

 correlated with these main features, and thus form 

 natural groups. 



There are two cotyledons in Dicotyledons as a 

 general rule, except in some Ranunculaceae, and a 

 few isolated types, whilst Sweet Gale (Myrica Gale) 

 has more than two. 



In Dicotyledons the embryo is provided with two 

 cotyledons, and the plumule is central, the cotyledons 

 lateral, the radicle opposite the plumule and below. 

 The leaves are usually net-veined. The stem struc- 

 ture shows secondary thickening, and the wood 

 consisting of ducts and fibres surrounds a central 

 pith, the wood being further arranged in concentric 

 rings, and a new layer is added each year to the 

 outside. There are medullary rays radiating from 

 the centre. The bark is increased by new layers on 

 the inside. The flowers have the parts in whorls or 

 a perianth of five, or four, or two members, rarely in 

 threes. 



The system of classification used in this country 

 is that of Bentham and Hooker, based on those of 

 De Candolle and Jussieu. As the arrangement 

 of Engler, which takes into better account the 

 anomalous Apetalae, is being more generally used, 

 a summary of it is given at the end of Volume 

 IIL 



