1064 REroRT— 1898. 



of auxospores follows by internal necessity. But it needs still more exact investi- 

 gation, for it is quite possible that the formation of auxospores, like the formation 

 of zygotes of the Desmidiace;e, is essentially dependent upon external conditions. 

 In that case there would be no definite alternation of generations in theDlatomese. 



4. In a number of Thallophytes, some few Chlorophycere, above all, in the 

 Floridete and Ascomycetes, a fruit arises from the fertilised ovum, or a body 

 homologous with it, which produces, in a manner peculiar to it, non-sexual cells, 

 the spores. This spore-bearing fruit may be compared with the sporogonium of 

 the Mosses, and the alternation of the sexual plant with the spore-fi'uit may be 

 regarded as an antithetic alternation. Ijut this comparison does not extend further 

 than the establishment of a certain analogy. 



In the two series of the Florideoe and Ascomycetes, in contrast to the series of 

 the Mosses, it appears that the fruit in the higher forms becomes constantly more 

 dependent upon the mother-plant, and that the duty of higher differentiation of 

 the fruit falls essentially upon the latter. The fruit there appears not as a special 

 generation, but as a product of the mother-plant. 



What, then, remains from which to derive the alternation of generations of the 

 Mosses and Ferns ? Only Coleochcete, which, since Pringsheim's celebrated in- 

 vestigation, has been quoted as a connecting link between Algae and Archegoniatse. 

 But it has never been proved that the zoospores of the germinating oospore are to 

 be regarded as a characteristic product of the fruit, and, accordingly, as a form of 

 propagation homologous with the Moss-spores. But, on the other hand, it makes 

 no great demand on our imagination to figure to ourselves how, in the Coleochcete- 

 like ancestors of the Mosses, this step was taken, that then the second step con- 

 sisted in the formation of stationary spores arising by a tetrad division. With 

 such assumptions, the transition to the simple Liverworts — e.g., Riccia, does not 

 appear very great, and, starting from this form, the different series included in the 

 Bryophyta may be derived. Thouoh we have thus gained certain connecting 

 points for the phylogeny of the Mosses, the question as regards the Ferns, in 

 which the fertilised ovum develops into the leafy plant, is in quite another 

 position. It has been recognised on many sides how great a contrast there is 

 between Mosses and Ferns. The common peculiarity in the structure of the 

 Archegonium might be a purely parallel development without its necessarily 

 indicating any phylogenetic connection. It is not my purpose to enter now upon 

 these difficult questions, the less so since they will be dealt with here from an 

 official quarter. They deal with the most interesting, but also the most obscure, 

 points in the phylogeny of the vegetable kingdom. For the spot where the first 

 indication of a Fern-sporophyte appeared was the birthplace of the vastly- 

 developed series of the Phanerogams. The Thallophytes hitherto known do not 

 give the least clue to the discovery of that spot, 



(c) The Formation of the Zygospore in Polyphagus Euglense. 

 By Harold Wager. 



1. This rare organism is found as a parasite on Euylena viridis. The material 

 for this inve.stigation was found with Euglense on a filter bed at Keighley in 

 Yorkshire, and cultivations were made in which the methods of spore formation 

 and zygospore formation were observed from the beginning to the end. 



2. The vegetative cell contains a single nucleus of large size and somewhat 

 peculiar structure. 



3. In the process of zygospore formation a rhizoidfrom the receptive cell comes 

 into contact with the discharging cell. The latter is nearly always larger than the 

 former, and contains a larger nucleus. 



4. The end of the rhizoid in contact with the discharging cell swells up and 

 becomes the zygospore. The small nucleus from the receptive cell passes into it 

 first of all together with the protoplasm, and then the large nucleus of the 

 discharging cell makes its way through the opening between the cells into the 

 zygospore also. 



5. The two nuclei come into close contact with one another, but do not fuse. 



