. The origin of a land flora, a theory based upon the facts of alternation. Plant morphology. MATONINEAE 567 Sporangia in which the annulus is not tilted are shown in Figs. 317 a, c ; from these it will be seen that the annulus starts close to the stalk; it first curves downwards towards the basiscopic side of the sporangium, then circling round it, curves upwards, the highest point being reached at the distal end of the sporangium; passing this it again curves down wards towards the basiscopic side, and stops short at some distance from the stalk; it is at this point that the dehiscence takes
. The origin of a land flora, a theory based upon the facts of alternation. Plant morphology. MATONINEAE 567 Sporangia in which the annulus is not tilted are shown in Figs. 317 a, c ; from these it will be seen that the annulus starts close to the stalk; it first curves downwards towards the basiscopic side of the sporangium, then circling round it, curves upwards, the highest point being reached at the distal end of the sporangium; passing this it again curves down wards towards the basiscopic side, and stops short at some distance from the stalk; it is at this point that the dehiscence takes place, but though the cells immediately beyond the end of the annulus may show some regularity of division, there is in Matonia no highly specialised stomium as is the case in most Leptosporangiate Ferns. Fig. 317 (the central. Fig. 317. A, B, C and the central figure represent the mature sporangia in various aspects. ^=young sorus; /, z'=indusium ; j=sporangium, j£= sporangium with cap-cell; «=acroscopic, ^-basiscopic side. Z?=sporangium with tapetum doubled. A-Cxso. D-Fxzoo. figure) shows the rupture; it also shows a case of the annulus stopping short of the stalk on either side, and that there is not here any continuous series of non-indurated cells, such as that seen in Loxsoma. Thus Matonia has a sporangium with a short and massive stalk and a large head, in which the annulus is not of a highly specialised, nor «ven of a constant type, though in its main features it corresponds to that of the Gleicheniaceae. It differs here, however, in its variability, its lateral dehiscence, and in the comparatively small output of spores. Of the fossil Matonineae the sori are' best known in Laccopteris, which is practically identical with Matonia in the size, disposition, and structure of the sporangia and spores, but differs in having apparently no indusium (Fig. 318). Probably, however, the sori of Matonidium and of Microdictyon. Please note that these images ar
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