198 Transactiojis. 



of the year. The outer zone of the cortex is noteworthy, and may 

 be compared with that in the rhizome of L. fast igiat urn. It consists 

 of a rather loose tissue of small roundish thin-walled parenchyma, three 

 to five cells in width, showing air-spaces, and bounded externally by 

 an epidermis which is only slightly cuticularized. There are abundant 

 stomata present. In some places this aerating tissue seems to be in process 

 of breaking down, while there are quite lengtliy stretches in which there is 

 seen to be the same development of enormously large irregular-shaped cells 

 separating the outer from the main cortical zones, as also occurs in L. fasti- 

 giafum. It is possible that in L. scariosum this is an adaptation for 

 aeration purposes, and that in L. fastigiatum is still persists although the 

 rhizome has become subterranean. The subterranean habit has probably 

 arisen as a modification from the epigaeous trailing stem, and there is no 

 doubt that it is not an absolutely fixed character, as is seen from the case of 

 L. densum. However, a simpler explanation is that in both L. scariosum and 

 L. fastigiatum the peculiar large-celled tissue functions as a water-reservoir. 

 As in the other three species, the aerial branches show a stellate configu- 

 ration, and there is no modification of the stele in the strobili or in the 

 heterophyllous regions of the plant. 



There is thus seen to be a very characteristic form of stele in all 

 the species which belong to the section Clavata. This type of stele gives 

 evidence of a greater degree of modification than do the other two main 

 types which occur in the genus. The habit and external form of these 

 species also present the greatest degrees of modification, and it is obvious 

 that the stelar anatomy is in direct correspondence with the habit. The 

 four New Zealand species show some small but interesting peculiarities 

 which can all be best explained by reference to the environmental factors. 

 The stem-anatomy of this section of the genus is thus seen to be in a plastic 

 condition, and some very interesting experiments could be conducted 

 (though perhaps with difficulty) to determine whether or not these modi- 

 fications are fixed characters. Whether or not the dorsiventral type of 

 stele covers but a single cycle of natural affinity in the section can only be 

 determined by a full study of the other main characters of the species 

 concerned. 



The Prothallus. 



The prothallus throughout this section is large, compact, long-lived, and 

 more or less deeply buried, and in its wholly saprophytic habit is clearly the 

 most modified of all the Lycopodium types. There are two main types of 

 this form of prothallus — viz., the clavatum type and the comjAanatmn type ; 

 and of the seven species of this section whose prothalli are known five 

 conform to the clavatum type and two to the complanatum type. Bruch- 

 mann (5, 6) has described the prothalli of L. clavatum, L. annotinum, and 

 L. complanatum, and Lang (24) that of L. clavatum. Spessard (25, 26) 

 has recently given a preliminary account of the prothalli of L. clavatum, 

 L. complanatum, L. annotinum, and L. obscurum as they occur in America. 

 The prothalli of the New Zealand species L. voluhile and L. scariosum 

 have been described by Miss Edgerley (12), by Chamberlain (7), and by 

 myself (15, 16). I have also described (16) the prothallus of the other 

 New Zealand species, L. fastigiatum. 



These types of deeply buried prothalli, living under consistent conditions, 

 do not show in any individual species such a range of variability as do 

 those forms of prothallus which can reach the surface. In fact, the main 

 variations from the normal which I have met with are related to the actual 



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