688 SUMMARY OF CURRENT RESEARCHES DELATING TO 



The agcidiospores give rise to binucleate uredospores mycelia and 

 finally to binucleate teleutospores ; as these latter mature, the two nuclei 

 in each cell become fused, and produce on germination the uninucleate 

 sporidia and uninucleate mycelium of the early ascidiuin stages. The 

 author considers that the migration of nuclei observed in the eecidium is 

 a reduced form of fertilisation ; though conjugation does not take place, 

 there is association which give the necessary sexual stimulus to further 

 growth. The spermogonia are male organs, that have become function- 

 less ; the nature of the spermatia proves this to be the case. Comparing 

 the development with that of the higher plants, he finds a clear alter- 

 nation of generations ; the sexual or gametophyte bearing spermogonia 

 and secidia, and characterised by a single nucleus, and the sporophyte or 

 asexual stage, bearing asexual spores, secidiospores, uredospores and 

 teleutospores. Finally in the teleutospore there is the return to the 

 oophyte, fusion of the nuclei, and reduction of the chromatin masses. 

 The teleutospore represents the spore mother-cell, and undergoes a 

 process of tetrad division to form the four cells of the promycelium. 

 These four cells are really spores, and are easily recognised as such in 

 forms like Coleosporium. The absence of the aecidium in the life-cycle 

 corresponds to the cases of apogamy observed in the higher plants. 

 Apospory is found in Enclophyllum, where the Eecidiospores behave on 

 germination like the teleutospores, and produce sporidia. Blackmail 

 has given full accounts of the cytology throughout. He compares the 

 fusion of nuclei in the basidiospore with fusion in the teleutospore, but 

 he would consider the Basidiomycetes, while closely related, to be 

 reduced apogamous forms of the Uredinese. 



Nuclear Phenomena in Coleosporium Sonchi-arvensis.* — R. J. 

 Holden and F. J. Harper selected this form, parasitic on various com- 

 posites, as favourable for the study of nuclear division and nuclear 

 phenomena. The authors consider the uredospores of this fungus to be 

 really ascidiospores — thus regarding Coleosporium Sonchi-arvensis as 

 monoecious. All other forms investigated have been found to be 

 hetercecious. They discuss the work already done by Sappin-Trouffy, 

 Dangeard, Poirault, etc., on this subject, and give in detail the results 

 arrived at in their own investigations. They lay special stress on the 

 fusion of the nuclei in the teleutospore, which has, they consider, " the 

 essential characteristics of a sexual fertilisation in the origin of the 

 nuclei, and in the behaviour of the teleutospores after fusion." In this 

 genus the teleutospore germinates at once, and sporidia are produced, 

 which are at first uninucleated. The nucleus divides in the sporidium, 

 and the cells of the fungus, according to these writers, are thenceforth 

 bi-nucleated until the teleutospore is again reached. Poirault and 

 Raciborski found in the division stages of the nucleus that there were 

 two chromosomes. Holden and Harper have evidence that there are 

 from six to ten. 



Witches'-Broom caused by Puccinia.f — P. Magnus has followed 

 the development of Puccinia Riibsaameni on Origanum vulgare, where 



* Trans. Wiss. Acad. Sci. Arts and Letters, xiv. (1904) pp. 63-80 (2 pis.). 

 f Ber. Deutsch. Bot. Gesell., xxii. (1904) pp. 344-7 (1 pi.)- 



