46a 



VASCULAR CRYPTOGAMS. 



inner and an outer cell, so that at this stage the young prothallium consisted of four 

 short cells forming an axial row terminated above by the apical cell, below by the 

 basal cell, and enclosed laterally by two rows of cells. It was impossible to trace 

 the development any further. Fifteen years later (1872) Fankhauser found in 

 Switzerland completely developed prothallia oi Lycopodium annotinum among some 

 Mosses, one of which was still connected with the young plant of the second 

 generation (Fig. 326). These prothallia, which had grown in the absence of light, 

 were irregularly lobed masses of cells of a pale yellow colour, furnished sparingly 

 with small root-hairs. On the upper surface were numerous antheridia which are 

 ovoid cavities in the tissue of the prothallium covered by a single layer of cells and 

 filled with the very numerous mother-cells of the anthero- 

 zoids. The form of the antherozoids themselves was not 

 very clearly made out. These prothallia had no longer 

 any archegonia, but they bore young plants : hence it ap- 

 pears that Lycopodium produces only one kind of spores, a 

 conclusion which is quite in accordance with the results of 

 direct observation, and that the prothallia are monoecious, 

 a peculiarity which at once sharply distinguishes the Lyco- 

 podiceae from the Isoeteas and Selaginellese, as does also 

 the very considerable size attained by the prothallium and 

 its complete independence of the spore. Probably these 

 conditions are the same in those genera which possess but 

 one kind of spores, Psilotum, Tmesipteris, Phylloglossum. 

 The prothallia of Lycopodium evidently bear several arche- 

 gonia, for Fankhauser found on them young plants in 

 various stages of development. From the attachment of the 

 young plant to the prothallium, it appears that the arche- 

 gonia lie upon its upper surface in the grooves between the 

 lobes. 



2. The Asexual generation (Sporophore). From what has 

 already been said it is evident that nothing is known con- 

 cerning the development of the embryo. The young plants 

 which Fankhauser found were attached to the prothallium 

 by means of a small projection, about the size of a pin's 

 head inserted into its tissue. This projection arises at the 

 side of the base of the stem and of the first root ; it evidently corresponds to the foot 

 of Ferns. 



The habit of the mature plants is very various in the different genera. Some 

 species of Lycopodium have an erect stem and erect branches (Z. Selago), in which 

 case the roots arising from the lower part of the stem often grow downwards within 

 it and issue in a tuft from its base (Z. Phlegmaria, ulicifolium, &c.). Very frequently 

 the main stem and its largest branches creep upon the earth, sending out roots here 

 and there into the soil, only certain branches, more especially those which bear the 

 sporangia, being erect. In these forms there is a tendency towards bilateral 

 organisation, which finds expression more particularly in the structure of the axial 

 fibrovascular mass. In all species the stem is thickly covered with small, narrow, 



FIG. -i-id.— Lycopodium a7ino- 

 tinum, after Fankhauser; p the 

 prothallium, I the young plant ; 

 •w its root (natural size). 



