ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 745 



classification. These are generally the form and size of the reproductive 

 organs. He finds, however, that all these are subject to considerable 

 variation, and chiefly the conidia, which differ in size and in appearance, 

 varying from smooth to distinctly echinulate. These phenomena are 

 not confined to the AspergiUaceae, and should have an important bearing 

 on the determination of species. 



Study of Nuclear Divisions in Rusts.* — Edgar W. Olive gives a 

 short preliminary sketch of the views held by successive workers on the 

 origin of the binucleated condition of cells of the Uredinese up to the 

 date of Blackmail's and Christman's papers on the subject. These two 

 writers disagree as to the explanation of the conjugation process ; 

 Blackman holding that it is oosporic, a large female cell receiving the 

 nucleus from a smaller male cell. Christman views it as zygosporic, 

 consisting of the union of two equal gametes, and resulting in a non- 

 resting zygospore. Christman finds also that nuclear migration occurs 

 in Puccinia PodophyUi in the teleutospore sorus, when there could be no 

 sexual process, and he is inclined to interpret all such migrations as 

 pathological. A history of work on nuclear division is also given. 



As a result of his own work, chiefly on Triphragmium ulmarw, 

 Olive concludes that the fusing gametes, as well as the nuclei, are 

 approximately equal, corresponding thus to Christman's view, and he 

 regards the upper sterile cell as merely a degenerating tip-cell, and 

 rejects Blackmail's interpretation that it is an abortive trichogyne. 

 Conjugation of the two gametes takes place through a larger or smaller 

 pore. He also found multinucleate cells at the base of the ascidium 

 cup, which Blackman considered abnormal ; as he has detected them in 

 eight or ten species of rusts, he concludes that they are of regular 

 occurrence, and are the result of repeated nuclear division without cell- 

 formation. He suggests that they belong to the sporophytic generation, 

 and arise owing to the stimulated growth that follows the sexual cell- 

 fusion. 



The vegetative nuclear division is constantly mitotic, each nucleus 

 apparently in entire independence of its associated neighbour. He was 

 unable to count the chromosomes in the dividing nucleus, but the 

 chromatic radiations, which are regarded as corresponding to the 

 chromosomes, are eight in number, and are segregated into two groups 

 of four, each group being attached to a distinct centrosome, thus giving 

 a double character to the daughter-nucleus. 



Uredinese. — Alfred Hasler f publishes a preliminary notice of his 

 work on the Puccinice of Crepis and Centaurea. In the former genus 

 he worked with about twenty species, making inoculation cultures with 

 different forms of Puccinia. Some of these grew on a number of Crepis 

 species such as P. praecox, others, such as P. Grwhcti, were specialised 

 to one species alone. Similar cultures were carried on with Centaurea, 

 and the results are shortly given. 



P. Dieteli describes a second series of Uredinese from Japan and 



* Ann. of Bot. xxii. (1908) pp. 331-60 (1 pi.). 

 + Centralbl. Bakt,, xxi. (1908) pp. 510-11. 

 1 Ann. Mycol., vi. (1908) pp. 222-9 (1 fig.). 



Dec. 16th, 1908 3 D 



