284 Transactions. 



the protophylls are all developed from the top of the protocorm, so 

 that there is no noticeable lateral extension of the latter (figs. 79-81). 

 In one or two instances, however, out of a great number of young plants 

 examined I observed that there Avas a certain amount of lateral growth, 

 the latest-formed protophylls occupying a position not on top of the 

 protocorm, but at the side of it farthest from the foot. One young 

 plant showed seven protophylls in all on such an extended protocorm 

 before a stem-axis had been initiated. Plate XVIII, fig. 1, is a photo- 

 graph of a section of a young plant whose protocorm has thus grown 

 sideways. In this particular plant the stem-axis had already been 

 initiated on the end of the protocorm farthest from the first-formed 

 portion, but it is not included in the section. The first root had 

 also appeared, and is shown in the jDhotograph. There is a dis- 

 tinct differentiation to be observed in the body of this protocorm 

 between the protocorm proper and the laterally extended portion. As 

 a rule, however, the protophylls are aggregated on the summit of the 

 protocorm, and after a certain number have been developed — generally 

 four or five — the stem-apex appears amongst them at the base of several 

 rapidly growing new protophylls. At the same time that the stem-ape_ 

 is initiated a finger-like protuberance appears in that region of the 

 protocorm which lies immediately below the position of the stem, and 

 grows outwards and downwards (fig. 79). A longitudinal section of the 

 young plant shown in fig. 79 revealed the fact that vascular tissues 

 were already developing from the stem-apex, and were declining into 

 the root-like protuberance at a slight angle. A photograph of this is 

 given in Plate XVIII, fig. 2. The section shown in this photograph 

 is not exactly median either for the stem-apex or for the root-apex, 

 but it shows the course of the vascular strand, and also the position 

 of the first root on the protocorm. The root-apex was protected 

 by a cap of cells which had originated from periclinal divisions in 

 the outer layer of cells of the apex. In the growing plant new leaves 

 are rapidly developed from the stem-apex, and a stem-axis is formed 

 (fig. 80). Subsequently formed roots emerge either at the base of the 

 stem through the tissues of the protocorm (fig. 80) or higher up the 

 stem (fig. 81). The protocorm can be distinguished at the base of 

 young stems which are from 1 cm. to 3 cm. in height. As in L. laferale, 

 the prothallus does not persist after the first two or three protophylls 

 have developed. 



L. densum. 



As has been stated in a preceding section of this paper,' I have not 

 been able to discover more than a single young plant of this species. 

 This was a plant about 4^ in. in height, erect, and branched above. 

 One other developing plant was also discovered in the same patch of 

 damp moss, but this was older, and had already assumed the creeping 

 habit. These young plants occurred in the immediate vicinity of adult 

 plants of L. densum, and there were no other species of Lycopodium to be 

 seen in the neighbourhood. On the first-named " seedling " plant a large 

 firm foot was jDresent at a depth of about 1 in. below the surface of 

 the ground (fig. 82). The first root was borne at the base of the stem, 

 and an adventitious root on the stem itself a short distance above the 

 foot. Longitudinal sections through this foot failed to reveal any 

 vascular tissue passing into it from the main stele. The main body 

 of -the foot consisted of large-sized parenchymatous cells, and there was 



