Müller[732] has recorded some observations on the pycnidia and stylospores of the Strigulaceae, a family of tropical lichens inhabiting the leaves of the higher plants. On the thallus of _Strigula elegans_ var. _tremula_ from Madagascar and from India, he found pycnidia with stylospores of abnormal dimensions measuring 18-26 µ in length and 3 µ in width, and with 1 to 7 cross septa. In _Strigula complanata_ var. _genuina_ the stylospores were 2-8-septate and varied from 7-65 µ, in length, some of the spores being thus ten times longer than others, while the width remained the same. Müller considers that in these cases the stylospore has already grown to a septate hypha while in the pycnidium. As in the pycnidiospores, described later by Hedlund, the spores had germinated by increase in length followed by septation. The spermogonia of _Strigula_, which are exactly similar to the pycnidia in size and structure, produce spermatia, measuring about 3 µ × 2 µ, and it is suggested by Müller that the stylospores may represent merely an advanced stage of development of these spermatia. Both organs were constantly associated on the same thallus; but whereas the spermogonia were abundant on the younger part of the thallus at the periphery, they were almost entirely replaced by pycnidia on the older portions near the centre, only a very few spermogonia (presumably younger pycnidial stages) being found in that region. Lindsay[733] has described a great many different lichen pycnidia, but in many instances he must have been dealing with species of the “Fungi imperfecti” that were growing in association with the scattered granules of crustaceous lichens. There are many fungi—Discomycetes and Pyrenomycetes—parasitic on lichen thalli, and he has, in some cases, undoubtedly been describing their secondary pycnidial form of fruit, which indeed may appear far more frequently than the more perfect ascigerous form, and might easily be mistaken for the pycnidial fructification of the lichen. G. GENERAL SURVEY _a._ SEXUAL OR ASEXUAL. It has been necessary to give the preceding detailed account of these various structures—pycnidia or spermogonia—in view of the extreme importance attached to them as the possible male organs of the lichen plant, and, in giving the results obtained by different workers, the terminology employed by each one has been adopted as far as possible: those who consider them to be sexual structures call them spermogonia; those who refuse to accept that view write of them as pycnidia. Tulasne, Nylander and others unhesitatingly accepted them as male organs without any knowledge of the female cell or of any method of fertilization. Stahl’s discovery of the trichogyne seemed to settle the whole question; but though he had evidence of copulation between the spermatium and the receptive cell or trichogyne he had no real record of any sexual process.