424 PART III. THE CLASSIFICATION OF PLANTS. 



L. Phlegmaria, where the oospore is divided by a transverse basal wall, the cell 

 next to the neck of the archegonium being the hypobasal cell, and the lower cell 

 the epibasal. The hypobasal cell developes into a short, cylindrical, usually 

 unicellular, suspensor. The somewhat hemispherical epibasal cell becomes seg- 

 mented into four octants by two walls at right angles to each other and to the 

 basal wall, and then the octants are divided transversely, by a wall at right angles 

 to the two preceding, into two tiers or stages of four cells each. Of these two 

 tiers the lower forms a short hypocotyl (as in Salvinia, see p. 412) which is com- 

 monly (but erroneously) called the foot, though it is morphologically quite 

 different from the foot of the Filichice and Equisetinse, the true homologue of 

 the foot in those groups being the suspensor in this. The upper tier of cells 

 gives rise to the first leaf or cotyledon, and to the primary stem. The first root 

 eventually springs adventitiously from cells belonging to the upper tier, below 

 the cotyledon : its origin is exogenous. 



In the other species which have been studied (L. cernuum and immdatuvi), 

 whilst the early stages are probably much the same as in L. Phlegmaria, some 

 important differences become apparent later. The primary stem is not imme- 

 diately developed, as in L. Phlegmaria, but in its place a tuberous protocorm 

 (closely resembling that of Phylloglossum) is produced, carrying the cotyledon 

 and other subsequently developed leaves, on its summit, and bearing adven- 

 titious roots of exogenous origin at its base : the proper primary stem is 

 eventually developed at the summit of the protocorm. 



Nothing is known of the embryogeny of Phylloglossum. 



Vegetative Propagation. In the creeping forms, as the main stems die off the 

 younger branches become independent and constitute new individuals. In 

 some species there are gemmae, as in L. Selago, where they are borne on the 

 stem, and are modified leafy branches; and as in L. cernuum, where they are 

 small tubercles, closely resembling the tuberous embryonic protocorm, and are 

 borne on the roots. 



THE GAMETOPHYTE. In so far as the gametophyte has been investigated, it 

 is a monoecious prothallium, either containing chlorophyll (L. inundatum and 

 cernuum), or destitute of chlorophyll (L. annotinum and Phleymaria) and sapro- 

 phytic. The gametophyte of Phylloglossum is unknown. 



The contents of the germinating spore (in L. inundatum) undergo division 

 into two cells : of these the one, the hypobasal cell, representing the root- 

 portion of the gametophyte, contains no chlorophyll, and merely grows some- 

 what without undergoing division : the other, epibasal, contains chlorophyll 

 and, lupturing the exospore, grows and divides to form the shoot of the game- 

 tophyte, the further development of which is effected for a time by an apical 

 cell, and subsequently by marginal growth. 



The morphology of the prothallium offers considerable variety. In L. inun- 

 datum and cernuum the prothallium is tuberous (see Fig. 276) ; its base is em- 

 bedded in the soil, and bears root-hairs ; its apex projects above the surface 

 and bears a tuft of green leafy lobes : the sexual organs are developed in a zone 

 from a layer of tissue which long remains merismatic and which is situated just 

 below the apical tuft of lobes ; occasionally some antheridia are developed on 

 the lobes. In L. annotinum the prothallium is also tuberous : it is somewhat 

 ovoid in form, bearing root-hairs on its lower surface, and reproductive organs 



