M. A. Braun on the Nucleus of the Characese. 299 



is of extremely simple nature, and remains enclosed at the bot- 

 tom of the archegonium, without freeing itself from its coats. 

 "From the Mosses with the simplest structure of the fruit, 

 finally," continues Hofmeister*, in his description, " it is only 

 one step to the Characese, in which the influence of the sperma- 

 tozoid on the central cell of the archegonium does not lead to 

 the production even of the simplest kind of cellular mass, but 

 merely to the filling up of the reproductive cell found free in 

 that central cell, with starch and oil. The Charce, in which the 

 prothallium is the entire plant, thus represent one end of the 

 series, the other end being formed by the Phanerogamia (exclu- 

 sive of the Coniferse), in which the whole plant corresponds 

 solely to the second spore-producing generation of the Vascular 

 Cryptogamia, and the cell-formation in the embiyo-sac previous 

 to the impregnation scarcely even reminds vis of the multifold 

 vital phsenomena of the prothallia of the Ferns and of the albu- 

 men mass of the Coniferse." 



For the further elucidation of the relations in which the Cha- 

 racese stand to the i-est of the Cryptogamia possessed of anthe- 

 ridia and archegonia, we must in the first place accurately exa- 

 mine whether they really have these two distinct generations, 

 even with ever so slight a development of the second, to which 

 the transition from the first is caused by impregnation, or whe- 

 ther they complete their entire cycle of life in one generation 

 (leaving ramification- generations out of view). According to 

 Hofmeister's description, there is found in the central cell of the 

 archegonium of the Characese, a new cell, the development of 

 which into the spore containing oil and starch is dependent on 

 impregnation. If this be the condition, if that which is found 

 in the central cell is a mere spore, there is in fact no alternation 

 of generations, but only one generation, for the spore in this case 

 is the primary cell of a generation which essentially resembles 

 that by which it is produced. If we compare, then, the one ge- 

 neration of the Characese with the first of the higher Ciypto- 

 gamia, especially with the prothallium of the Vascular Crypto- 

 gamia, Hofmeister's interpretation appears warranted on one 

 side, in so far, namely, that the structure of the Characese termed 

 an archegonium is a female organ (receiving impregnation), 

 borne by the prothallium, but, on the other hand, unsupported, 

 since this does not produce any second, spore-bearing generation, 

 but merely a spore. But if the comparison with the archegonium 

 is nevertheless to be maintained, we must extend it to organs 

 through which the spore-formation is brought about in the 

 lower (leafless) Cryptogamia, an extension for which many 



* Flora, 1851, No. 1. p. 7- 



21* 



