42 THE OPHIOGLOSSALES 



and there is no connection between it and the tissues of the stem apex of the bud. 

 The latter consists of a shallow mass of tissue with the conspicuous apical cell in 

 the center, but below it there is no sign of the development of any procambium. 

 The stem apex lies in a depression formed by a shallow ridge, which encircles it 

 and forms the beginning of the stipular sheath belonging to the base of the leaf. 

 The exact limits of the basal tissue of the leaf, as we have already stated, can not 

 be clearly defined. The cavity above the stem apex is still very evident, but how 

 much of the tissue lying above the cavity belongs to the leaf base, and how much to 

 the cortical tissue, is not clear. The section through the apex of the leaf (fig. 25, 5) 

 shows a single large terminal cell which, without doubt, is the apical cell. 



The young bud is now ready to emerge and, very soon after, the rapidly elongat- 

 ing apex of the young leaf pushes through the outer root tissue and emerges upon 

 the outside. The stem apex remains buried within the root tissues and the sheathing 

 base of the leaf. The leaf base is surrounded by a ragged sheath, formed by the 

 ruptured outer tissues of the root. 



The development of the bud upon the root in 0. pendulum unfortunately could 

 not be followed. The smallest leaves found were 10 centimeters or more in length, 

 and, although these were probably the primary leaves, they were not recognized as 

 such at the time the plants were collected, and so there was no opportunity of tracing 

 their connection with the original root. 



The fully developed cotyledon in what may be considered the typical form of 

 O. moluccanum is more or less lanceolate in outline (fig. 22, Z)). There is a central 

 vein from which branch secondary veins on either side, connecting with the central 

 vein by anastomosing branches which inclose elongated meshes. In the form with 

 broader leaves, probably another species, the mid-vein is more obscure and the 

 meshes are broader and more numerous. 



Three types of the embryo may be recognized in Ophioglossum, represented 

 respectively by 0. moluccanum, O. vulgatum, and 0. pendulum. If, as seems not 

 unlikely, O. moluccanum is the most primitive of the three, some interesting points 

 arise as to the significance of the peculiarities exhibited by the embryo, which shows 

 only two organs aside from the foot, viz, the cotyledon and primary root, these 

 growing in an almost exactly opposite direction, without any clear line of demarca- 

 tion between them. I have ventured to draw a comparison between the sporophyte 

 of Ophioglossum and that oi Anthoceros, assuming that the former has arisen from 

 some bryophytic type not unlike Anthoceros, by the development of a root from the 

 base of the sporogonium and of a special foliar organ from the basal meristem of 

 such a sporogonium. The embryo of O. moluccanum approaches this hypothetical 

 form, as it consists only of leaf and root, and no stem apex is developed from it, 

 its growth being of limited duration. In this case the definitive sporophyte is a 

 secondary structure developed as a bud upon the primary root. In 0. vulgatum, 

 however, the definitive stem apex, although of very late origin, is apparently a 

 product of the original embryonic tissue, but the first foliage leaf is of much later 

 origin. In 0. pendulum the formation of the leafy sporophyte is also secondary, 

 but neither stem apex nor leaf is developed from the embryo itself 



If, as the writer believes, Ophioglossum represents the most primitive type of 

 the fern series, it is quite conceivable that in O. moluccanum and its allies the embryo 

 represents the condition existing in the ancestral type from which these have sprung. 

 On the supposition that the leafy sporophyte is derived from a large bryophytic 

 sporogonium resembling that oi Anthoceros, there must have been a stage when the 

 sporophyte consisted of two parts only, the upper sporogenous portion, which later 

 developed into a sporophyll, as represented in Ophioglossum, and the root. Of 



