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singular provision is necessary, as the plant is frequently 

 exposed to dry air, which absorbs the moisture on the 

 surface of its native soil, and would consequently wither 

 it, were it not furnished with radicles, which penetrate 

 beyond the risk of desiccation. There are some very 

 curious and little-known green algae allied to this plant, 

 which are furnished with similar adaptations, as their 

 fronds are so incrusted with lime as to render nutriment 

 through the surface precarious. They resemble cacti, reti- 

 culated corals, flabelliform corallines, little wheels fixed 

 on delicate stems, etc., and are very beautiful in their 

 shapes or in their structure, when divested of the car- 

 bonaceous coating in which they are masked. Caulerpa, 

 Halimeda, Acetabularia, etc., are examples of these curious 

 organisms, which might easily be overlooked as corals. 

 They are all natives of warm climates, such as New 

 Zealand and Papua. In pools and ditches of fresh water 

 may often be seen vast masses of the two-pronged fila- 

 ments of Vaucheria dichotoma, each filament being some- 

 times two feet long, almost rivalling the huge masses 

 of Cladophora mirabilis, and the Conferva melagonium 

 of the Arctic regions. It differs little from the Botrydium, 

 except that the spherical vesicle of the latter is elongated 

 into a simple or branched thread. Another species is 

 very common on the ground in damp, dark situations, 

 such as the ledges and crevices of cliffs in sub-alpine 

 glens, and is also occasionally observed in gardens on walls 

 or unfrequented walks, creeping over the earth in a very 

 thin intricate fleece of a bright grassy-green colour. The 

 filaments are tubes containing an internal green pulveru- 

 lent mass like the other confervse ; but the fructification 



