234 Transactions. 



Details of the Fungus. 



There is not very much to say here with regard to the details of the 

 symbiotic fungus in these three species of prothalli. The hyphal coils are 

 present only in the epidermal cells of the fungal region, although the hyphae 

 penetrate farther into the adjoining tissue in an intercellular position. 

 I have seen no formation of clusters of "spores" as occurs in the epiphytic 

 prothalli. Spores occur, however, in the interior tissue of the protocorm of 

 the young plant along with hyphae in between the cells. 



One prothallus of L. ramulosum showed in its lower basal tubercle a 

 number of large, spherical, dark-staining bodies, three of which are illus- 

 trated in fig. 75. These bodies possessed thick walls, and in section were 

 seen to be full of numerous very small oval lightly-staining " spores." My 

 serial transverse sections of this tubercle showed that there were no fewer 

 than twelve of these large bodies present. They lie within the cell-cavities 

 in the region in which the fungus is intercellular. Each is large enough 

 to completely fill a cell and bulge out its walls. In each of two other 

 prothalli of this species I observed a single spore body of this nature. 

 I was not able to determine their nature, but jiidge that they bear some 

 relation to the symbiotic fungus. 



General Remarks. 



A special interest attaches itself to the study of the prothalli of the 

 different species of Lycopodium, arising mainly from the fact that several 

 types of prothallial structure are represented in the genus, and also that 

 each of these types goes hand in hand with certain characteristic features 

 in other organs of the plant. So different are these types of prothalli one 

 from another that both Treub and Bruchmann have expressed the opinion 

 that these differences date from a very ancient period. Treub states his 

 belief that they can be explained in a small degree only by the different 

 conditions under which the prothalli live. Bruchmann would divide the 

 genus into as many new genera as there are distinct prothallial types. As 

 opposed to this view, Lang has suggested that the different prothalli show 

 a similarity in ground plan, and that they are all more or less profound 

 modifications of an original cermium-like form. As further species of 

 prothalli are found this interest is deepened, for it becomes clear that 

 although the main types are all now probably known to us, yet there are 

 many significant modifications of them, and also that further study of the 

 genus will probably reveal more such. Instead of assuming that the 

 different prothallial types are practically unrelated, it will probably be 

 more productive of results to try to discover from the development of the 

 individual prothalli and from their variations whether there is a funda- 

 mental plan of structure, and what has been the reason for its modification. 

 Such a study will, at all events, help us to recognize which characters are 

 of most importance. 



The complete mature prothallus of all the sections of the genus except 

 the Inundata and Cernua shows consistently at its basal, original end the 

 form of an inverted cone, the apex of the cone being occupied by a single 

 cell, to which the remains of the spore can sometimes be seen attached. It 

 is, of course, possible that in some cases a brief filamentous stage may arise 

 first from the spore before the cone form is attained, and that this drops 

 away later and so becomes lost, but apparently it seems that the cone form 

 is at once initiated. In the much-branched prothalli of the Phlegmaria 

 type, which are radial in build but not upright in growth, the cone quickly 



