CHAP, v.] RELATIONSHIP AMONGST PLANTS. 181 



lilies, hyacintlis, tulips; Oraminece, grasses, including 

 bamboos, sugar-cane, and the various cereals, as wbeat, 

 rice, oats, maize, etc. ; Orchidece, orchids ; Irideoe, iris, 

 gladiolus, etc. ; AmaryllideoB, snowdrop, daffodil, snow- 

 flake, etc. 



The plants belonging to the order Aroideas, including 

 our " lords and ladies " {Arum maculatum) and the Nile 

 lily {Richardia cethiopica), have the veins of the leaves 

 forming a network as in Dicotyledons. 



II. Dicotyledones. 



Fibro-vaacular bundles open, arranged concentrically. Embryo with 

 two opposite cotyledons. Whorls of flower in fives or multiples of 

 five ; rarely in multiples of two. 



The leaves in the present group attain a much higher 

 degree of specialization than in the Monocotyledons, and 

 there is a perfect sequence in the various species, from 

 the uncut simple leaf with an entire margin to the much 

 divided compound leaf possessed of the power of closing 

 and thus protecting its working surface when conditions 

 are unfavourable for the performance of its functions. 

 Protection against climate is often present in alpine or sub- 

 arctic species under the form of a dense coating of inter- 

 woven hairs, giving to the leaf the appearance of felt. In 

 the majority of species the leaves, whether simple or com- 

 pound, are articulated to the branch from which they 

 spring, and at the end of the season at once fall off, 

 leaving a clean leaf-scar on the branch. In " evergreen" 

 plants the leaves live for a longer period than one 

 season, and do not all fall away at one time, but the 

 old leaves fall away after new ones have become fully 

 developed. The modifications of leaves into tendrils, in 



