Organography of plants, especially of the archegoniatae and spermaphyta . , and the envelope which grows out only after fertilization theperianth. Many Hepaticae have only a perichaetium, others, like Hymenophytum, have also aperianth. DISPOSITION OF SEXUAL ORGANS 83 exists^, its place is taken by the concave curvature of the sexual shootitself. In Symphyogyna (Fig. 71) the group of archegonia is protected bya single scale-like growth of the thallus which forms a perichaetial scale,whilst the antheridia stand singly, covered over by a small scale on thedorsal side of the thallus. This position
Organography of plants, especially of the archegoniatae and spermaphyta . , and the envelope which grows out only after fertilization theperianth. Many Hepaticae have only a perichaetium, others, like Hymenophytum, have also aperianth. DISPOSITION OF SEXUAL ORGANS 83 exists^, its place is taken by the concave curvature of the sexual shootitself. In Symphyogyna (Fig. 71) the group of archegonia is protected bya single scale-like growth of the thallus which forms a perichaetial scale,whilst the antheridia stand singly, covered over by a small scale on thedorsal side of the thallus. This position I assume to be the original onefor the archegonia. The behaviour of Morkia points in this direction. Init there are, outside the perichaetium, some single scales ; whilst in Blyttiathese are united more or less to a scale-like envelope. Such a homologycan only hold, however, within one genus or within a very near cycle ofaffinity, and in other Hepaticae the perichaetium arises certainly in anotherway than by the union of scales. In Pellia, at least in P. calycina. the. Fig. 72. Sphaerocaqjus terrestris. Portion of a female plant seen from above. Many perichaetia, eachsurrounding one archegonium, cover almost the whole surface of the thallus. Magnified 12. perichaetium is like that of Blyttia, only that its mouth inclines towardsthe apex of the thallus, as there is formed, not only behind the. archegonialgroup, reckoned from the vegetative point, but also /;/ front of it, a growthwhich after fertilization grows out strongly and forms with the scales theenvelope of the sporogonium. The combination of the archegonia in groups increases evidently theprobability of fertilization. Usually only a single embryo develops intoa sporogonium, and this bores into the tissue underneath the archegonium ;in P. calycina 1 have occasionally found two sporogonia within one envelope,but they were unequally developed. This is at least the case in Metzgeria furcata. According to Stephani, Hepaticae
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