Many modern lichenologists reject the view that they are sexual; they regard them as secondary organs of fructification analogous to the pycnidia so abundant in the related groups of fungi. One would naturally expect these pycnidia to reappear in lichens, and it might be considered somewhat arbitrary to classify pycnidia in Sphaeropsideae as asexual reproductive organs, and then to regard the very similar structures in lichens as sexual spermogonia. It has also been pointed out that when undoubted pycnidia do occur on the lichen thallus, as in _Calicium_, _Strigula_, _Peltigera_, etc., they in no way differ from structures regarded as spermogonia except in the size of the pycnidiospores—and, even among these, there are transition forms. The different types of spermatia can be paralleled among the fungal pycnidiospores and the same is also true as regards the sporophores generally. Those described as arthrosterigmata by Nylander—as endosporous by Steiner—were supposed to be peculiar to lichens; but recently Laubert[734] has described a fungal pycnidium which grew on the trunk of an apple tree and in which the spores are not borne on upright sporophores but are budded off from the cells of the plectenchyma lining the pycnidium. It may be that future research will discover other such instances, though that type of sporophore is evidently of very rare occurrence among fungi. _b._ COMPARISON WITH FUNGI. The most obvious spermogonia among fungi with which to compare those of lichens occur in the Uredineae where they are associated with the life-cycle of a large number of rust species. They are small flask-shaped structures very much like the simpler forms of pycnidia and they produce innumerable spermatia which are budded off from the tips of simple spermatiophores. The mature spermatium has a delicate cell-wall and contains a thin layer of cytoplasm with a dense nucleus which occupies almost the whole cavity, cytological characters which, as Blackman[735] has pointed out, are characteristic of male cells and are not found in any asexual reproductive spores. If we accept Istvanffi’s[736] description and figures of the lichen spermatia as correct, their structure is wholly different: there being a very small nucleus in the centre of the cell comparable in size with those of the vegetative hyphae (Fig. 115). [Illustration: Fig. 115. _a_, spermatia; _b_, hypha produced from spermatium of _Buellia punctiformis_ Th. Fr. × 950 (after Istvanffi).]