INTRODUCTION 
of the digestive juices of animals. Some seeds of dehiscent fruits are more 
or less surrounded by a fleshy outgrowth known as an aril, which is often 
brightly coloured, as in the Spindle-tree, and serves as an attraction to 
birds ; others, such as those of Willows, Poplars, and Willow-herbs, are 
furnished with tufts of hair, which are known as a coma, and aid 
considerably in the dispersal of the seeds hy wind. 
Internally, one of the most important differences between seeds is 
whether they contain a food-store or albumen apart from the embryo or 
young plant, when they are termed albuminous, as in Buttercups, Pinks, 
and most Monocotyledons ; or whether the embryo entirely fills the seed, 
which is then termed exalbuminous, as in Orchids, Crucifer ce, Leguminosce, 
Composite, etc. The albumen may be starchy or oily, mealy or horny ; 
and the embryo may occupy various positions with regard to it, being 
coiled round it in the Pink Family and lying at one side of its base 
in Grasses. 
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