OPHTOGLOSSACE.E. 



3«' 



the next older one, as shown in Fig, 283 in the case of Botrychium Lunaria. lii 

 Ophioglossum the relative positions of the parts at the end of the stem are still more 

 complicated, from the fact that the rudimentary leaves, while completely enclosed 

 one ^vithin another, produce ligular structures which grow together so completely 

 that each leaf appears as if enclosed in a kind of chamber formed by the cohesion 

 of the ligular parts of leaves of different ages, recalling a similar structure in Marattia. 

 These cohesions however leave an opening at the apex 

 of each chamber ; the apex of the stem is therefore ex- 

 posed to the air through a narrow canal (Hofmeister). 



As soon as the leaves have attained a certain age, 

 each leaf bears a collection of sporangia, which form a 

 branch springing from the axial side of the leaf (in O. 

 palmatum two or more such 'fertile segments' are formed). 

 In the genus Ophioglossum both the outer sterile and the 

 fertile branch of the leaf are unbranched or only lobed 

 {0. palmatum) \ in the genus Botrychium both are again 

 branched and in parallel planes (Fig. 282, A and B). 

 The earlier hypothesis of a cohesion of the two leaf- 

 stalks of a fertile and of -a sterile leaf is at once nega- 

 tived by the history of development (Fig. 283), and 

 would lead to very complicated theories of stem-branch- 

 ing, of which we have no evidence. The history of de- 

 velopment rather indicates, as Hofmeister first showed, 

 that the receptacle originates on the inner side of the leaf. 

 In the mature state the fertile leaf-branch eiUier separates 

 from the sterile (green) one at the base or at the middle 

 of the lamina {0. pendulum)^ or the two branches of the 

 leaf appear as if separated deep down to their origin 

 (6^. bergianum), or, finally, the fertile branch springs from 

 the middle of the leaf-stalk {^Botrychium rutafolium and 

 dissectinii). 



The Spora?igia of the Ophioglossaceae are so essen- 

 tially different from those of Ferns and Rhizocarps that 

 these plants cannot, for this reason, be arranged in either 

 of these classes ; whether they differ as greatly from those 

 of the Equisetacege and Lycopodiacese is yet to be proved 

 by the history of their development. They agree 



with the sporangia of all Vascular Cryptogams in the one point of belonging to 

 the leaves. The history of their development is not yet accurately known ; but 

 from the half-ripe states which I have been able to examine in B. Ltmaria and 

 0. vulgatum, it is evident that the sporangia cannot be products of single epidermal 

 cells, as in Ferns and Rhizocarps, but that their origin more resembles that of the 

 pollen- sac of the anthers of many Angiosperms. Each sporangium is, in Botry- 

 chium, an entire lobe of a leaf, the inner tissue of which produces the mother-cells of 

 the spores. A longitudinal section through the unripe so-called spike of 0. vulgatum 

 (Fig. 284) shows that the outer layer of the wall of the sporangium is a continuous 



Fig. 284. — Longitudinal section 

 through the upper part of a spike 

 of Ophioglossian vttlgaUan : s 

 its free apex, sp the sporangia! 

 cavities, r the part where they 

 burst transversely; ^ the fibro- 

 vascular bundles (x about lo). 



