1 74 Transactions. 



more or less sclerenchymatous, the middle delicate and spongy, and the 

 very narrow inner zone small-celled. The walls of the inner layer of the 

 latter are usually slightly cutinized. One or more roots are to be seen in 

 transverse section at the base of the stem of all the varieties mentioned. 



On the other hand, the stelar anatomy of the epiphytic L. Billardieri 

 corresponds very closely with that of the largest varieties of L. varium 

 described, albeit on a still larger scale. A transverse section of the lower 

 imbranched portion of the stem of this species is shown in fig. 7. It will 

 suffice to draw attention briefly to the fact that in this case we have an 

 extreme illustration of the tendency to the grouping of the xylem and the 

 phloem in temporary islands and curving bands which is to be observed in 

 all the large stems of the species of the Phlegmaria section. There is an 

 extensive development of large metaxylem, and most of the phloem groups 

 and bands show large centrally -placed empty sieve tubes. The inner layer 

 of the middle cells of the cortex have obviously cutinized walls, there is a 

 .spongy middle zone of thin-walled parenchymatous cells with copious air- 

 spaces, and the epidermal cortical zone is strongly sclerenchymatous. At 

 the extreme base of a large stem as many as six roots are to be seen in 

 transverse section in the middle cortex. The root stele as seen in the stem 

 cortex is of the typical form so consistent right through both Selago and 

 Phlegmaria sections — viz., a single large crescentic group of xylem with 

 the bay between the two horns occupied by a single phloem group. The 

 root originates from the stem stele by the giving-off of two groups of xylem 

 from two adjacent plates and of a group of phloem from the intermediate 

 phloem plate, the two xylem groups almost immediately joining to form 

 the single crescentic group. 



The stele of the delicate plant named L. Billardieri var. gracile 

 corresponds exactly with that of the smaller forms of L. varium. This is 

 shown in fig. 8. The configuration of the stele is variable, at one time the 

 plates of tissue being strictly radial, and at another a continuous plate 

 either of xylem or phloem extending right across the stele. In the lower 

 part of the stem one or two roots are to be seen penetrating the middle 

 cortex. 



From the study of the chain of forms which occur in New Zealand 

 connecting L. Selago through L. varium with L. Billardieri it will be seen, 

 first, that there is a definite type of stelar anatomy characteristic of the 

 whole series, and, secondly, that a gradual change takes place in the 

 vascular arrangement from a strictly radial form in the smaller-growing 

 .species to a form in larger species in which the radial or stellate arrange- 

 ment is broken up by cross connections, which result in the isolation of 

 some of the xylem and phloem into islands. Moreover, there is a well- 

 marked and gradually increasing tendency in larger and larger forms to the 

 differentiation of the phloem into sieve tubes and phloem parenchyma. This 

 is quite in accord with Jones's description (21) in his study of the anatomy 

 of the stems of twenty species of Lycopodium. In the case of L. serratmn 

 Thunb. and L. reflexum liam., both of which species belong to the L. Selago 

 cycle of affinity, Jones's figures of the stem stele show that along with the 

 fact that in general habit the two species named grow more robustly than 

 L. Selago the arrangement of the vascular tissues is no longer simply radial, 

 but the general configuration of the more abundant xylem and phloem is 

 broken up by cross connections, with the consequent formation of phloem 

 islands. His figures of the stele of the strongly growing epiphytic species 

 L. squarrosum. Forst., L. Dalhousieanum Spring, and L. Phlegmaria Linn 

 are closely similar to that of the large New Zealand epiphytic L. Billardieri. 



