192 Transactions. 



are scrambling over scrubby vegetation the adventitious roots are some- 

 times of great length. They may be as much as 3 ft. to 5 ir. in length, and 

 a very characteristic feature during the wet season is the thick envelope 

 of mucilage which covers from 3 in. to 12 in. of the growing root-tip before 

 it reaches the ground. This mucilage envelope also occurs to a much less 

 extent on the exposed root-tips of such other species as L. cernuum, L. 

 densum, L. scariosum, and L. fastigiatum. The spikes are of a very charac- 

 teristic form, which may be regarded as a direct adaptation in accordance 

 with the scrambling habit of the plants. They are produced only when the 

 plant can raise its lateral branches to a considerable height, and then the 

 ultimate twigs on the entire terminal portion of such a branch become 

 developed as long cylindrical pendulous strobili. Plate XII, fig. 2, A, shows 

 a portion of such a fertile branch, at the point where the ordinary foliage 

 passes into the fertile region. The terminal portion of the branch has 

 been broken off at the point marked with a cross. Frequently on such 

 branches fertile regions are intermixed with sterile, and tnce versa, as 

 also will be clearly seen in the figure. A close comparison may be insti- 

 tuted between the fertile region of this species and that of the pendulous 

 epiphytic species of the Phlegniaria section, the obvious deduction being 

 that in both cases the form of the strobilus is simply the result of the 

 pendulous habit, and that the Lycopodium strobilus must be in a very 

 plastic condition for this habit to appear in the Clavata section. 



The main stem of L. densum is subterranean, but sometimes — as, for 

 example, at the edge of a bank — it emerges from the ground and continues 

 its growth, becoming green in colour. The aerial branches arise right and 

 left of the main rhizomes, and at once bend sharply upwards, emerging 

 from the ground with a stiff, erect, dendroid habit. There are three very 

 distinct forms of aerial branches, which take their character from the 

 nature of their foliage. These are shown in Plate XIII, at A, B, and C, that 

 lettered B showing its own particular form of foliage in the upper portion 

 of the branch and the foliage of form A in the lower portion. These .three 

 varieties of foliage are almost invariably quite distinct from one another, 

 and do not grade into one another, being confined for the most part to 

 separate branches. Where more than one variety does occur on the one 

 branch, as in the specimen figured, the two forms nevertheless keep quite 

 distinct. Now, all three varieties of foliage are commonly to be met with 

 in practically every locality where L. densum occurs, growing side by side, 

 so that it is obvious that the different forms are not by way of being 

 adaptations to the environment. It would seem, then, that they are 

 hereditary polymorphs, true-breeding races which possibly have arisen by 

 mutation, and which hybridize. These three forms are by no means 

 plastic in their nature, although individual twigs may very occasionally be 

 observed which seem to show gradations in their foliage. When growing 

 amongst tangled vegetation, more especially in hollows, the aerial branches 

 may attain a great height. They are then very scantily branched ; indeed, 

 I have seen aerial stems as much as 9 ft. in height, some of which have been 

 quite unbranched. The cones are very numerous, are short, and are borne 

 solitarily at the tips of the ultimate branchlets very much after the same 

 manner and appearance as in L. cernuum. Instances are to be met with 

 sometimes in which there has been a vegetative prolongation of the cone, 

 as at the points marked with a cross in Plate XIII, D. In this particular 

 figure the lower of the two fertile regions thus indicated may well have been 

 differentiated after the whole twig had been formed. 



