224 Transactions. 



Another type of massive prothallus is that shown in figs. 58 and 59, 

 where the continued bulky growth has resulted in a very irregular form. 

 The oldest part of the prothallus can be recognized in both these figures, 

 although whether or not this part represents the actual original basal end of 

 the prothallus cannot be said. In fig. 58 there are two distinct generative 

 regions, the uppermost of which is divided by a deep constriction. The 

 foot of a young plant has been torn from one portion of this upper region. 

 This particular prothallus is similar in its continued growth to those shown 

 in figs. 52-54, except that the great bulkiness has rather obscured the 

 typical cylindrical radial build. In fig. 59 the prothallus has grown still 

 more irregularly, and there are apparently two growing regions, one of 

 which is broken. The sexual organs are distributed along the whole of the 

 top of the prothallus, and are in this case archegonia only. This particular 

 prothallus is best compared with the basal portion and first generative 

 region only of those shown in figs. 53 and 54. These massive, irregularly- 

 grown prothalli usually show abundant chlorophyll. 



Position in the Soil. 



All the prothalli in these three species are situated at the surface of the 

 soil and possess more or less chlorophyll. Their position in the soil is always 

 erect. The chlorophyll is never present in the basal regions, but always 

 in the lobes, and generally also in the upper part of the shaft. Consequent 

 on this vertical position of growth, the prothalli never show such an 

 elongated habit as do those of the epiphytic, subterranean type, but certain 

 individuals, especially in L. ramulosum, show a marked tendency in this 

 direction. I cannot say whether or not the more elongated forms in this 

 species are more deeply buried in their basal part than the massive forms. 

 They were all dissected out of humus consisting for the most part of a 

 decaying short moss. In any case, the total length of even the most 

 elongated forms is too small to have much significance in this respect. 

 Probably the function of continued apical growth is due simply to the 

 postponement of the formation of the embryo, the food-supply being 

 maintained by the fungus through the infection of newer regions of the 

 prothallus. The typical radial build is maintained by all these three species, 

 although in some prothalli, more particularly in L. ramulosum, this is almost 

 obscured by the adoption of a secondary, irregular manner of growth. 



Early Stages in the Development. 



I have been fortunate to secure several very young prothalli of the two 

 species L. laterale and L. ramulosum. No doubt the only perfectly satis- 

 factory way of obtaining the youngest stages of growth in any prothallus 

 is by the experimental germination of the spores in the laboratory under 

 close observation. Even this method, however, is not above suspicion, 

 for one can never be sure to what extent the artificial conditions influence 

 the form of the young prothallus. Very young prothalli dissected out of 

 soil collected in the field are open to the criticism that they may belong 

 to some plant other than the one under consideration. I can only say 

 that with regard to the young prothalli now to be described I am quite satis- 

 fied that they belong to the particular species of Lycopodium to which I 

 have ascribed them, and the reasons will be stated. 



In the case of L. cernuum, I have found no young stages. Treub has, 

 however, described the germination of the spore in this species, having 

 successfully carried this out in the laboratory. His figures, which I have 



