194 Transactions. 



on the ventral side. The stages in the development of this form of dis- 

 tichous arrangement can also be seen in the young plants, but not so well 

 as in L. volubile, since the heterophylly is developed rapidly and very early. 

 When growing in dry situations — as, for example, at considerable altitudes — 

 the lateral branches of the mature plant of L. scariosum are more or less 

 flattened in the j)lane of the ground, but when amongst other vegetation 

 they tend to assume a more upright position. This species occurs in wide, 

 luxuriant spreads around the abandoned gold-mining claims throughout 

 north Westland, and there the lateral branches are characteristically erect- 

 growing, although the heterophylly is still strongly marked. Frequently, as 

 a result of the upright habit of growth, the twigs of these branches show an 

 all-round spread, and even the flattened falcate leaves are more outstanding, 

 but inspection shows that both twigs and leaves arise in the characteristic 

 dorsiventral manner. The long club-shaped cones are borne in great num- 

 bers, being raised up on pedicels 3 in. to 6 in. in height, which are formed 

 by the continued growth of the main twigs of the branch. The appear- 

 ance of these pedicels previous to the formation of the cones is very 

 striking, standing stiffly up as they do in massed numbers above the dense 

 foliage. The gradual transition from heterophylly to the spiral arrange- 

 ment of ordinary acicular leaves can be well seen at the base of these 

 pedicels. When growing amongst ferns and saplings at the edge of the 

 forest, the lateral branches of this species sometimes become very long- 

 drawn-out and adopt a semi-scrambling habit. Owing to the rapid growth 

 the scale leaves are somewhat scattered along these branches, and in those 

 regions in which the characteristic heterophylly has appeared its develo])- 

 ment has taken place irregularly. Instances are not infrequently met with 

 of internodes showing, contrary to the usual rule, one, two, or even three 

 dorsaljy placed orthostichies of scale leaves, the type of heterophylly then 

 approximating to that of L. volubile. 



Stem-anatomy. 



As in the case of the two other natural divisions of the genus, the 

 Clavata section shows a very characteristic and consistent type of stelar 

 anatomy. This has been described by Jones (21) in the six species 

 L. clavatum, L. annotinum, L. complanatum, L. chamaecyparissus, L. alpinum, 

 and L. obscurum ; by Boodle (2) in L. volubile; and by myself (15, 16) in 

 the four New Zealand species which belong to this section. The central 

 cylinder consists throughout of parallel plates of alternating xyleni and 

 phloem disposed dorsiventrally, surrounded by a pericycle. Consequent on 

 the comparatively large size of the plant in the New Zealand species, 

 the number of plates of vascular tissue is also large. The phloem is 

 markedly differentiated into centrally-placed empty sieve tubes of large 

 size and flanking phloem parenchyma with abundant contents. I have 

 previously described (15) in L. volubile and L. scariosum the development 

 of the dorsiventral structure characteristic of the mature stele from the 

 radial structure characteristic of the young plant, showing that it is initi- 

 ated in the developing plant at the point of branching, which in this section 

 of the genus always takes place in the plane of the ground, and tends 

 thereafter to be preserved in between the branchings. Assuming that this 

 is the main cause of the dorsiventral structure, it is quite possible that 

 it will be found in species which are not closely related, and thus this 

 character taken by itself will not be a sure sign of natural affinity. Owing 

 to the great plasticity of the genus Lycopodium as seen in all its main 



