HoLLOWAY. — Studies in the New Zealand Species of Lycopodium. 213 



structure exhibits modifications in the different sections of the genus which 

 are quite in accord with the conditions under which the prothalli of those 

 sections live. There is no need for the surface-growing prothalli of 

 L. Selago to increase in length, for they soon reach the light. Nor is 

 there any great storing-up of food in their tissues, for the young plant 

 when formed can quickly attain independance. Again, it is probably the 

 inherited tendency towards the chlorophyllous, self-nourishing condition, 

 which is strong in the prothallus of this species, which causes the more 

 deeply buried individuals to adopt the peculiar and extensive prolongation 

 of the upper margin of the cone into the cylindrical, bilateral, erect branches 

 in the effort to reach the light. In the altogether subterranean humus- 

 loving prothalli of the Phlegmaria section the chlorophyllous habit has 

 been completely lost, and the direction of growth of the prothallus bears 

 no relation to the surface of the soil. These prothalli are greatly elongated 

 and branched, and the extensive development of long rhizoids, as in the case 

 of the humus-growing prothalli of Tmesipteris .and Psilotum, shows that it 

 is necessary for the fungus in the prothallus to be brought into intimate 

 contact with as large an area as possible of the humus for its nourishment. 

 The method of elongation is here altogether different from that adopted by 

 the underground prothalli of L. Selago. Starting from the cone form, the pro- 

 thallus quickly passes into the cylindrical form without increasing its girth, 

 the meristem continuing in the original apical position throughout the life 

 of the prothallus. In this way the main prothallus body is formed, that of 

 L. Billardieri var. gracile being more elongated than that of the other-species 

 examined. The somewhat liulky nature of the forward generative portion 

 of this body of tissue goes hand in hand with the need for the prothallus 

 to support the young plant for a longer period than in the case of the 

 prothallus of L. Selago, owing to the correspondingly greater depth at which 

 the former is buried. The lateral branches arise adventitiously from any 

 part of the main prothallial body and grow from an apical meristem. 

 They are primarily vegetative, the sexual organs being borne normally 

 on the central body. The latter in its generative region possesses a 

 bilateral structure which is always dorsiventral, the sexual organs being 

 borne only on the upper side. Here again this is not strictly comparable 

 with the bilateral structure of the processes of the L. Selago prothallus, 

 for in the latter it is, according to Bruchmann, simply carried over from 

 the margin of the original basal cone and always bears evidence of this. 

 Thus the modification of the original cone form in the epiphytic prothalli, 

 as in those of L. Selago, is best explained in the light of the conditions 

 under which the prothalli live. 



The structure of the prothallus in the New Zealand species belonging 

 to the Cernua section, and the modifications which there occur, will be 

 considered in the next section of this paper, and a general comparative 

 survey, including also the structure of the prothallus of the clavatum and 

 complanatum types, will be instituted in the concluding remarks. 



Section Cernua. 

 L. cernuum Linn. ; L. laterale R. Br. Prodr. ; L. ramulosum T. Kirk. 



Literature. 



In 1884 Treub (13) published his account of the prothallus of L. cernuum. 

 Goebel's (5) account of the prothallus of L. inundatum followed next in 1887, 

 and in the following year Treub (15) described his laboratory cultures of 



