170 Transactions. 



as a variation from varium rather than from Billarclieri. The variety 

 gracile is always quite distinct from L. Billardieri, and it would be a more 

 startUng reversion from that species, with its very distinct strobili, than it 

 would be from L. varimn, which, as has been emphasized above, is not so 

 far removed from the Selago condition, imless, indeed, we are to take the 

 view that the whole genus is to be read as a reduction series. It may be 

 mentioned here that W. Colenso described the form now known as 

 L. Billardieri var. gracile under the name L. iiovae-zealandicum (11, p. 275), 

 noting that it grows as an ejjiphyte on fern-trees. He describes it as 

 " a small species of the Selago section, apparently pretty closely allied to 

 L. taxifolium Sw.," and he speaks of L. varium as being its nearest New 

 Zealand congener. 



Stem-anatomy. 



I wiU now pass on to consider the stem-anatomy of the mature plant 

 of the New Zealand species of the sections Selago and Phlegmaria. Here 

 also a high degree of plasticity will, be apparent, although the entire 

 subgenus Urostachya, so far as it has been investigated, can be seen to be 

 characterized by a consistent type of both stelar and cortical anatomy 

 which is markedly distinct from the type of stem-anatomy of any of the 

 other sections of the genus. 



It will be necessary to make first some general statements. Owing to 

 the plant being orthotropic in growth, of very limited size, and also more or 

 less branched, it will be clear that in comparing the anatomy of these species 

 care must be taken to section the different stems in corresponding parts of 

 the plant. At the extreme base of the stem the stele has not attained its 

 full development, and is also more disturbed by the giving-ofi of the roots 

 than it is above. The typical form of the stele is best seen a little higher up 

 the stem, though still in its lower half. Again, as is well known, the general 

 configuration of the xylem and phloem groups and plates is by no means 

 stable, even in a short length of the stem, so that it therefore becomes 

 necessary to compare a number of sections of the stem of any individual 

 plant in order to arrive at a fair idea as to its particular stelar anatomy. 



I hope to develop in this paper the conclusion, which I arrived at in a 

 previous paper (16, p. 302), that, notwithstanding the fact that the genus 

 Lycopodmm includes several distinct types of stelar structure and also 

 manifold variations of those types, yet the lines upon which the Lycopodium 

 stele has evolved can be recognized, having been determined for each 

 natural division of the genus by a combination of the inherited constitu- 

 tion with the acquired habit of growth of that division. Each of these 

 natural divisions shows a very distinct type of stelar and of cortical 

 structure, so that this character becomes of value in checking the con- 

 clusions arrived at from the study of the other characters as to which 

 section a particular species should be referred to. The sections Selago 

 and Phlegmaria possess a stelar structure of the stellate or radial type, 

 although at the extreme base of a plant this is sometimes obscured. The 

 protoxylem groups are very massive and the protophloem very small, 

 and except in the largest forms there is comparatively little wide-sized 

 metaxylem formed. The phloem also shows very little differentiation of 

 conspicuous sieve tubes in the smaller species. • 



Fig. 1 is a drawing of the stele of the Macquarie Island plant shown 

 in Plate IX, fig. 2, B, which has been identified by Cheeseman as 

 L. varium. The massive xylem bands radiate from a common centre, 

 which is occupied by large-sized metaxylem. The phloem is much less in 



