STRUCTURE AND AFFINITIES OF LEPIDOSTROBI. 



453 



The normal arrangement of the leaves of a plant is spiral around the 

 branch : when the latter is very short, and the leaves also short and 

 crowded, the whole branch becomes a cone ; this is frequently seen on 

 the apices of the branches of some plants, and is also artificially effected 

 in others, by an injury to the branch, which prevents its elongation. 

 In Tierra del Fuego there is a genus, several species of which have the 

 branches punctured by an insect ; the consequence is, that the wounded 

 portion is arrested in its tendency to prolong, the sap is thrown into the 

 leaves, which become broader and otherwise of different appearance 

 from the usual form of leaf, and lap over one another, so as to produce 

 a cone. 



I have thus long dwelt upon the formation of spurious cones, because 

 some of the so-called Lepidostrobi may be of this nature, — witness 

 the Lepidodendron oocephalum, * of which it is impossible to say 

 whether it be a Lepidostrohis or the apex of a branch crowded with 

 short leaves. 



The Fuegian plant mentioned above illustrates this subject, and a 

 wood- cut of two species of the genus alluded to (Pernettya, allied to 

 the " Heaths") is added. Both were collected at Cape Horn, where 

 the plants were invariably thus coniferous in the diseased branches, 

 while the healthy bore little bell-shaped flowers. Instances of this sort 



are not very uncommon on individual species, but a general tendency 

 in the development in question is sufficiently curious. Were the above 

 figured plants to occur fossil, the probability is, that their cones would 

 be regarded as the undoubted reproductive organs, and the plants 

 themselves be provisionally referred to Coniferas ; in further evidence of 

 which opinion the cold climate they inhabit might be adduced, and 



t. 20G. 



2 i2 



Lindley and Hutton, Fossil Flora, v. iii. 



