DICKSON I A. 



167 



Dennstjedtia (Denn-st£ed'-ti-a), Bernhardi and Moore, which possesses 

 the same distinctive characters as Patania. 



EuDiCKSONiA (Eu-dick-so'-m-a), of various authors, having a distinctly 

 two-valved involucre, the outer valve of which is formed by the apex of a 

 segment. 



Patania (Pat-an'-i-a), Presl, with a cup-shaped involucre, not at all, or 

 very indistinctly, two-valved. 



SiTOLOBiuM (Si-tol-ob'-i-um), /. Smith, a section of plants provided with 

 rhizomes (prostrate stems), and with a cup-shaped, nearly spherical involucre 

 placed at the base of the depression of the lobes. 



The genus Picksonia, as now accepted, contains about forty known 

 species of stove and greenhouse Ferns, the majority of which are native of 

 Tropical America and Polynesia. One species, P. puncHloba, however, reaches 

 as far north as Canada, and several others are scattered throughout the 

 northern parts of the Temperate zone ; but there are no British representatives 

 of the genus. About half the known species are of arborescent habit, and 

 in the countries where these are indigenous they form quite a distinct feature 

 in the vegetation with their immense yet finely-cut fronds, of a leathery 

 texture, under the shadow of which travellers often make a halt, sleeping 

 in blankets spread upon their gathered fronds. The others have creeping 

 rhizomes, and, with two exceptions, P. abrupta and P. Plwesii, all the 

 known species have their fronds at least twice divided to the midrib. 



Culture. 



The majority of the Dicksonias only require cool treatment ; most of 

 the arborescent kinds being found growing in valleys and in deep, shaded 

 ravines, and in countries where some of them occasionally have their fronds 

 heavily loaded with snow. P. antarctica, especially, grows in great abundance 

 on Mount Wellington, in Tasmania, where it is often subjected to a much 

 cooler temperature than that in which it is usually kept under cultivation, 

 and where it has, in fact, to mthstand somewhat severe fi-osts, although these 

 are only of short duration. This species thrives when planted outside in 

 sheltered spots in different parts of England, Wales, and Ireland. Wherever 

 a suitable spot exists, Tree Ferns should be introduced, as they present 



