ACOTYLEDONS. 59 



from parasitical by the fact that a?i epiphyte, though it grows 

 upon another plant, does not injure it by absorbing its sap or 

 otlurwise destroying it, as is the case with parasites like the 

 mistletoes. The staghorn and elkhorn ferns of New South 

 Wales and Queensland — so named from the shape of their 

 fronds — are epiphytes; and their handsome green leaves 

 agreeably relieve the dull hue of the stems on which they are 

 frequently found growing. The bird's-nest fern (Asplenium 

 nidus) is often found growing as an epiphyte. Epiphytal 

 ferns are not peculiar to the stems of tree ferns ; they grow 

 freely on other large trunks, deriving their nourishment 

 from the humidity of the atmosphere. Ferns are acrogenous — 

 that is, they increase their stems by the summit, the trunk 

 sometimes having the shape of a cylinder. Acrogens have 

 another very curious characteristic, a description of which 

 can only be understood after the student is thoroughly 

 grounded in that part of botany relating to the reproduction 

 of plants. 



Algae, the seaweeds, need not be described at length. 

 Many of the species are utilised for food and other useful 

 purposes ; and the same may be said of the mosses. 



Lichens include some of the lowest forms of vegetation ; 

 the variously coloured stains seen on rocks and buildings 

 are masses of lichens. Others hang like tufts or beards 

 from the branches of trees. 



Fungi are cellular plants, of peculiar construction. 

 Mushrooms belong to this sub-division ; so do most of 

 those destructive agents which attack grain crops and fruit 

 trees. Oidium tuckerii or vine disease, rust in wheat, and 

 ergot of rye are examples. Mould on cheese and bread 

 also belong to the fungi. 



