[Illustration: Fig. 106. Germination of multinucleate spore of _Ochrolechia pallescens_ Koerb. × 390 (after de Bary).] _e._ MULTINUCLEATE SPORES. These spores, which are all very large, occur in several genera or subgenera: in _Lecidea_ subg. _Mycoblastus_ (Fig. 105), _Lecanora_ subg. _Ochrolechia_ and in Pertusariaceae. Tulasne[677] in his experiments with germinating spores found that in _Lecanora parella (Ochrolechia pallescens?)_ germinating tubes were produced all over the surface of the spore (Fig. 106). De Bary[678] verified his observations in that and other species and added considerable detail: about twenty-four hours after sowing spores of _Ochrolechia pallescens_, numerous little warts arose on the surface of the spore which gradually grew out into delicate hyphae. All these spores contain fat globules and finely granular protoplasm with a very large number of minute nuclei; the presence of the latter has been demonstrated by Haberlandt[679] and later by Zopf[680] who reckoned about 200 to 300 in the spore of _Mycoblastus sanguinarius_. These nuclei had continued to multiply during the ripening of the spore while it was still contained in the ascus[680]. Owing to the presence of the large fat globules the plasma is confined to an external layer close to the spore wall; the nuclei are embedded in the plasma and are connected by strands of protoplasm. The epispore in some of these large spores is extremely developed: in some _Pertusariae_ it measures 4-5 µ in thickness. _f._ POLARIBILOCULAR SPORES. The most peculiar of all lichen spores are those termed _polaribilocular_—signifying a two-celled spore of which the median septum has become so thickened that the cell-cavities with their contents are relegated to the two poles of the spore, an open canal frequently connecting the two cell-spaces (Fig. 107). Other terms have been suggested and used by various writers to describe this unusual character such as blasteniospore[681], orculiform[682] and placodiomorph[683] or more simply polarilocular. The polarilocular colourless spore is found in a connected series of lichens—crustaceous, foliose and fruticose (_Placodium_, _Xanthoria_, _Teloschistes_). In another series with a darker thallus (_Rinodina and Physcia_) the spore is brown-coloured, and the median septum cuts across the plasma-connection. In other respects the brown spore is similar to the colourless one and possesses a thickened wall with reduced cell-cavities. [Illustration: Fig. 107. Polarilocular spores. _a_, _Xanthoria parietina_ Th. Fr.; _b_, _Rinodina roboris_ Th. Fr.; _c_, _Physcia pulverulenta_ Nyl.; _d_, _Physcia ciliaris_ DC. × 600.]