Organography of plants, especially of the archegoniatae and spermaphyta . entlygreat difference between germina-tion of the spore and the develop-ment of gemmae is conditionedpurely by the lie of the gemmaeas they are formed. In Lejeunia also if the outerconditions are not favourable pro-embryo and gemma grow into athallus before the leafy plant isproduced, and this is normally the case in an epiphyllous species of Lejeuniawhich I found in Java and named L. Metzgeriopsis (Fig. 93). This remark-able plant has a thallus which is richly branched and bears appendages atthe margin,—cell-rows which
Organography of plants, especially of the archegoniatae and spermaphyta . entlygreat difference between germina-tion of the spore and the develop-ment of gemmae is conditionedpurely by the lie of the gemmaeas they are formed. In Lejeunia also if the outerconditions are not favourable pro-embryo and gemma grow into athallus before the leafy plant isproduced, and this is normally the case in an epiphyllous species of Lejeuniawhich I found in Java and named L. Metzgeriopsis (Fig. 93). This remark-able plant has a thallus which is richly branched and bears appendages atthe margin,—cell-rows which arise in regular serial succession at the vegeta-tive point and may be considered as rudimentary leaves. This thallus,fastened firmly to the substratum by its rhizoids, propagates itself bygemmae. Leafy shoots appear as short appendages upon it, and thesehave the sole function of producing sexual organs, and their further vegeta-tive development is not possible so far as we know. The thallus is thennothing else than a giant pro-embryo possessing a peculiar vegetative. Fig. 93. Lejeunia Metzgeriopsis. Male plant. Descrip-tion in the text. Mag^niCetl! It is attached somewhat differently from tliat in Radula. no GERMINATION OF THE SPORES IN HEPATICAE body which elsewhere is only a rapidly passed over developmental Protocephalozia ephemeroides and amongst the Musci we shall findsimilar cases. In other Hepaticae, such as Lophocolea, Chiloscyphus, Calypogeia,and Cephalozia, the spores, which have a finely granular exosporium,produce in germination a tube which becomes a cell-row by the formationof transverse division-walls. It forms then, as in Aneura and Metzgeriaa cell-thread which may also branch, and it is of interest to note that in Calypogeia Trichomanes, for example, stagesof germination similar to those of Lejeunia appearoccasionally, that is to say, a cell-surface growingby means of a two-sided apical cell develops, andwe have here a proof that this is only a modi
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