296 TKANSACTIOICS AND PROCEEDINGS OF THE [Sess. LXiv. 



and of irregular and unsyrametrical outline ; others, again, 

 had a shape evidently a modification of the typical reniform. 

 In these last, along the adaxial side ran a deep vertical 

 groove, while the two ends of the horse shoe were, as it 

 were, pushed together so that an appearance was produced 

 of two small oval sporangia subtended by a single leaf. 

 This, which looked like a branching, was merely a lobing, 

 the cavities of the two lobes being continuous on the 

 abaxial side, and the two arising on one stalk. From 

 such a lobed condition to a complete branching would 

 be but a step, and in some of my preparations there 

 appears evidence that tliis step has been taken and that 

 branching does occur (Fig. 18, Plate III., a photo-micro- 

 graph of a longitudinal tangential section of a semi-sterilised 

 cone). Such an appearance as in this figure would be 

 produced, however, by a deeply lobed sporangium, if cut 

 in a particular plane, and I prefer to regard this as a case 

 of a very deeply lobed sporangium. 



From the above, it will be apparent that the capability 

 of variation in the strobilus and associated organs of 

 Lycapodium davatum is not inconsiderable. Thus, mer- 

 istic variations occur as branchings of the strobiliferous 

 axes and cones, in the size of the cones, in the size, shape, 

 and lobing of the sporangia, and in the point of origin of 

 the branches ; while homceotic variations appear in the 

 metamorphoses of cones into foliage shoots, complete or 

 partial, — in fact, all stages occur. 



The scheme of correlation of these various features 

 works out as follows : — 



JJranching of the. Strohilns is accompanied by (a) dimin- 

 ution in size of the main strobilus, as well as of its branch 

 or branches ; (b) variations in the sporangia, such as changes 

 in shapje and size, some being bulkier than normal and of 

 irregular shape, especially near the point of origin of 

 branches, others showing incipient branching. 



Sterilisation of the Strobilus is associated with (a) very 

 marked diminution in size — the sterile strobilus being 

 about half, or less than half, the normal length ; (&) 

 metamorphy of the sporophylls into foliage leaves — this 

 may occur before the sporangia disappear ; (c) variations 

 in the sporangia, such as occur in the branched strobilus. 



