112 THE OPHIOGLOSSALES 



After the separation of the fertile and sterile portions of the sporophyll the 

 sterile segment at first grows much more rapidly than the sporangiophore and soon 

 extends beyond it, so that the sporangiophore has the appearance of being merely 

 an adaxial appendage of the sporophyll. These changes in the relative importance 

 of the points can be very well shown by a study of the very large sporophylls of O. 

 pendulum. In this species the young leaf emerges from the sheath while it is still in 

 a very early stage of development. These young leaves (fig. 82) have a very thick, 

 fleshy leaf base, ending in the small pointed lamina, bent over and almost hiding the 

 young sporangiophore which is attached to its inner surface. This curved-over 

 form of the young sporophyll differs from that of Euophtoglossum^ where the young 

 leaf is straight, and in this respect there is a suggestion of Botrychium or of the 

 true ferns. The young spike at this stage is almost equal in length to the sterile 

 lamina. 



If the very young sporophyll of Ophioglossum moluccanum is examined, it will 

 be seen that the vascular bundle leaving it passes downward and joins a young root 

 trace. Very soon after the bundle enters the young leaf it divides into two branches, 

 one of which passes into the base of the spike and the other and larger one into the 

 sterile section of the sporophyll. This latter bundle now divides again into two, 

 one of which passes to the dorsal side of the sterile segment while the other is turned 

 toward the ventral side of the leaf, which probably represents tissue belonging to the 

 sporangiophore. In the cross-sections of older leaves the petiole, which includes 

 the completely fused base or peduncle of the sporangiophore, shows three distinct 

 bundles, a large abaxial one and two smaller adaxial bundles. The former remains 

 undivided for some distance above the base of the insertion of the peduncle of the 

 sporangiophore. The two adaxial bundles divide into several branches, this begin- 

 ning just below the point where the lamina of the sterile leaf becomes differentiated 

 from the petiole. The lamina has its edges infolded so that it has a conical form, 

 open in front and inclosing the young spike (figs. 56, 57). The successive branching 

 of the two adaxial bundles follows in quick succession, and the outer bundles con- 

 tribute to the veins of the lamina; the inner ones pass upward into the peduncle 

 of the spike. 



In a previous paper (Campbell 7) the conclusion was reached from the study of 

 a series of sections at different heights, taken from the full-grown sporophyll, that 

 the two adaxial bundles belonged exclusively to the spike. A study of the devel- 

 opment of the young sporophyll shows that this statement is not entirely correct 

 and that a considerable part of the vascular system of the sterile lamina owes its 

 origin also to branches from the two adaxial bundles before the latter enter the 

 peduncle of the sporangiophore. Of the two adaxial bundles, one represents the 

 original bundle of the sporangiophore derived from the primary forking of the leaf 

 trace; the other is derived secondarily from a subsequent division of the second 

 branch of the leaf trace, this also giving rise to the large abaxial bundle of the petiole. 



THE DEVELOPMENT OF THE SPORANGIUM. 



Much the most complete account of the development of the sporangium of the 

 Ophioglossaceae is that of Bower (Bower 5), who has made a very exhaustive exam- 

 ination of the development of the sporangium in all three genera. My own studies 

 have been for the most part confined to Ophioglossum pendulum, 0. moluccanum, 

 and Botrychium virgimanum. Burlingame (Burlingame 1) has more recently 

 examined the development of the sporangium in a species of Ophioglossum from 

 the Philippines, which was assumed to be 0. reticulatum. Beers (Beers 1) has 

 also published recently a somewhat incomplete account of the sporangium in Hel- 



