56 THE MORPHOLOGY OF PTERIDOPHYTES 



sporophylls are aggregated in the terminal regions of the 

 axes, yet they can hardly be said to constitute a strobilus, 

 for the sporophylls do not differ from the sterile leaves to 

 any marked extent. All the species of the Phlegmaria sub- 

 section are epiphytic. L. phlegmaria itself is illustrated in 

 Fig. 9K. The pendulous dichotomous branches terminate 

 in branched strobih in which the sporophylls are smaller 

 and more closely packed than the sterile leaves but, 

 nevertheless, afford relatively little protection for the 

 sporangia. 



The Inundata subsection of the Rhopalostachya is repre- 

 sented by the British species Lycopodium imindatum (Fig. 

 9D). Here, the strobilus is only slightly different in appear- 

 ance from the vegetative shoot, for the sporophylls (Fig. 

 9E) are only sUghtly modified for protecting the sporangia 

 (cf. sterile leaf. Fig. 9F). Within the Clavata subsection are 

 three more British species, L. annotimim, L. clavatiim and 

 L. alpinum, of which the first two are illustrated (Figs. 9G 

 and 9H). In this group, the sporophylls are aggregated into 

 very distinct strobili and are very different from the sterile 

 leaves, for they are provided with an abaxial flange (Fig. 9I) 

 which extends between and around the adjacent sporangia 

 belonging to the sporophylls below (cf. sterile leaf. Fig. 9J). 

 Whereas the strobih of L. annotinum terminate normal leafy 

 branches, those of L. claxatum are borne on specially 

 modified erect branches, whose leaves are much smaller and 

 more closely appressed. There are, thus, two different kinds 

 of sterile leaf in this species. The Cernua subsection includes 

 a number of species with very different growth habits. 

 L. cernuum has a creeping axis, from which arise at intervals 

 erect branch-systems resembhng tiny fir trees in being appar- 

 ently monopodial (for this reason sometimes called 'ground 

 pines'). In this species, all the sterile leaves are alike, but in 

 L. volubile (Fig. 9L) there are three or four kinds of sterile 

 leaves. It is a plant with a scrambhng habit and its main 

 axes are clothed with long needle-shaped leaves arranged 



