so 



OPHIOGLOSSACEAE 



[CH. 



Fig. 342. Ophio- 

 glossuni Bergi- 

 a;««/^^Schlecht. 

 (Whole plant, 

 slightly re 

 duced.) 



The genus Ophioglossum is a variable one, and to obtain a conception of it as a whole 

 other species than O. vulgatum must be examined. They are not all habitually mono- 

 phyllous : several small species bear a plurality of leaves, for instance 

 O. Bergianum (Fig. 342), where the spike is attached very low down on 

 the narrow leaf, and the sporangia are few. In O. crotalophoroides Walt, 

 four to six leaves may be simultaneously expanded, and this may go along 

 with a bulbous distension of the storage stock. This condition is most 

 frequent in small-leaved forms, and it may be held to connect the mono- 

 phyllous habit with the polyphyllous strobiloid construction common in 

 other Pteridophytes. But the genus also shows a capacity for amplification 

 of the parts of the individual leaf by branching beyond the typical simpli- 

 city, as is seen especially in O. penduhiin a.r\d pali/iatuin (Figs. 343, 344) : 

 somewhat similar branchings are not uncommon in O. vulgatum itself, 

 (Fig. 344,/, K) and other species. The large series of examples in Kew 

 and the British Museum illustrate how frequently forking is related to the 

 production of numerous spikes, or to the branching of the single spike : 

 while the position which the spikes hold is usually not marginal, though 

 this may occur occasionally. The majority of them are inserted upon the 

 upper surface of the sterile blade, while the lowest of them is commonly 

 nearest to the median line (compare Vol. I, Fig. 36, p. 30). 



There is a rough though not an exact parallelism between the number 

 of the fertile spikes on a frond and the number of the lobes of the sterile 

 blade. From 70 specimens of O. palmatum examined, ranging from those 

 with a single sterile lobe to eleven, and from one fertile spike to seventeen, the totals come 

 out as sterile lobes 328 and fertile spikes 373. This shows that there is a substantial paral- 

 lelism, though it cannot be pursued into numerical detail. It is plain also that the leaves 

 with the most lobes are those which are broadest : or speaking generally the number of 

 fertile spikes increases with the assimilating area. The morphology of the ophioglossaceous 

 spike will be discussed later (pp. 66, 87). Meanwhile it may be remarked that the facts for 

 Ophioglossum^ when a plurality of spikes is seen, do not appear consistent with any direct 

 recognition of their pinna-nature. They point rather to some hypothesis of chorisis of a 

 single original spike holding a median position ; and they suggest the view that in Ophio- 

 glossum the fertile spike, whatever its morphological origin may have been, had become 

 a morphological entity of the type seen in normal specimens of O. vulgatum^ and that this 

 was liable to fission and other morphological changes of form and of exact position. But 

 these changes are no more suitable material for direct argument as to the nature of the 

 spike than are the stamens or carpels of monstrous angiospermic flowers for the direct 

 elucidation of the morphology of those parts. 



Besides such amplifications within the genus there is also a line of simplification in 

 Ophioglosstim. It culminates in O. simplex Ridley (Fig. 345). This ground-growing 

 mycorhizic plant has tall fertile spikes without any sterile blades. Anatomically as well as 

 in form it resembles the epiphytic O. pendulum^ but it is closer still to the rare O. inter- 

 medium Hook, which is also a ground-growing species. It appears probable that O. simplex 

 forms the end of a series of reduction of the vegetative system consequent upon a myco- 

 rhizic habit and a shaded habitat. Here it would seem that the mycorhiza makes the 

 nutrition of the large spike still possible in the dense wet forest in which the plant grows, 

 notwithstanding that the usual assimilating organ is functionally absent. Reduction is, 

 however, not apparent in the large spike itself: for provided nutrition be kept up from 

 whatever source it would still retain its character, being essentially a spore-bearing organ. 



