60 SUMMARY OF CURRENT RESEARCHES RELATING TO 



BOTANY. 



GENERAL, 



Including the Anatomy and Physiology of Seed Plants. 



Cytology, 

 Including- Cell-Contents. 



Reduction-division and Synapsis in Spirogyra.* — A. Trondle has 

 studied the zygotes of three species of Spirogyra, i.e., S. neglecta, S. 

 calospora, and S. longata, with special reference to the reduction-division 

 and the fate of the four nuclei, resulting from the division of the 

 fusion-nucleus. In S. calospora and S. longata the nuclei resulting from 

 the first division contain the double number of chromosomes, the 

 reduced number appearing in the second division. In >S'. neglecta, the 

 first division shows the double number of chromosomes, but they are 

 arranged in pairs which unite at the poles to form single chromosomes. 

 The author regards the former type as pirimitive, and the latter as an 

 intermediate stage l)etween it and the conditions existing in higher 

 plants. It would appear as if the reduction-division can occur at differ- 

 ent stages in the development of the zygote ; in primitive types it 

 immediately precedes germination, in more advanced types it occurs 

 directly after fusion of the nuclei. Phylogenetically, Spirogyra is 

 derived from forms whose unicellular sporophyte produces the zygote 

 by the germination of four daughter-cells ; its sporophyte generation is 

 thus a reduced one, being more reduced than in such plants as the 

 Hydropterideffi, where four daughter-cells are still formed, although 

 only one develops. The zygote of Spirogyra is equivalent to both spore- 

 mother-cell and spore, the other stages being suppressed. Finally, the 

 author disagrees with those writers who regard the synapsis stages as 

 being of the greatest importance in mingling the parental chromatin 

 and in the formation of bivalent chromosomes ; the behaviour in Spiro- 

 gyra is contrary to this view. 



Structure and Development. 



Vegetative. 



Epiphytic BromeliaceaB.f— C. Picado contributes a note upon the 

 Bromeliaceae, which he regards as forming a very characteristic biologic 

 group. Most authors have regarded the leaves as simple reservoirs for 

 rain-water and dust ; the present paper maintains that, even if this were 

 the case, they would differ from such reservoirs among terrestrial plants : 

 (1) in their arrangement upon the branches, (2) their conditions of illu- 

 mination, (3) their reduced dimensions, (4) tlie purity of their water. 



* Zeitschr. Bot., iii. (1911) pp. 593-619 (5 pis. and 20 figs.). 

 t Comptes Rendus, cliii. (1911) pp. 9C0-63. 



