448 SUMMARY OF CURRENT RESEARCHES RELATING TO 



BOTANY. 



GENERAL, 

 Including the Anatomy and Physiology of Seed Plants. 



Cytology, 

 including- Cell-Contents. 



General Cytology.* — B. M. Davis continues his interesting " Studies 

 on the Plant Cell," in which he is giving a general resume and dis- 

 cussion of cell problems. In this part, No. 5 of the series, he deals 

 with cells-unions, and nuclear fusions in plants. 



Heterotype division.f — V. Gregoire and J.SBerghs J have made 

 further observations on the exact meaning of the first apparent split 

 which appears in the chromosomes of this division in microspore-mother- 

 cells. They believe that in synapsis two threads become arranged side 

 by side to form the thick spireme thread. The chromosomes are 

 thus double in nature, but duality is not produced by the bending on 

 itself of a segment of the spireme thread, as Dixon, Farmer and Moore 

 believe, or in other words the double chromosomes are produced by the 

 somatic chromosomes from the first lying side by side, not by these 

 chromosomes joining end to end and later bending over parallel to one 

 another. Berghs describes the process of formation of the double 

 spireme thread in detail in Allium fistulosum. 



Cell-Structure of the Cyanophycese.§ — Alfred Fischer has brought 

 forward a new work on this much-discussed subject. His most im- 

 portant points are that the " central body " contains large quantities of a 

 carbohydrate (derived from the chromatophore), either glycogen, or 

 anabamin which can be converted, at least partially, into glycogen or 

 dextrin by treatment with acid. The mitosis which was observed by 

 various workers is not a process by which chromatin is distributed to 

 the daughter-cells, but a mere equal distribution of granules of an inert 

 assimilatory product, or carbohydrates. The mitosis of the older 

 observers is thus nothing more than carbohydrate-mitosis (kohlehydrat- 

 mitose). The chromatin lately described by Olive, in the form of 

 chromosomes and threads, is nothing more than anabamin which takes 

 nuclear stains like chromatin. The interesting possibility that this 

 carbohydrate-mitosis is the phylogenetic forerunner of the nuclear 

 mitosis of higher plants, is suggested. 



Cytology of Araiospora.|| — C. A. King has investigated the cytology 

 of A.pulchra, a somewhat rare aquatic fungus first described by Thaxter, 

 and placed doubtfully either in the Peronosporacea? or Saprolegniaceas. 



* Aiuer. Nat., xxxix. (1905) pp. 217-68 (8 figs.). 



t La Cellule, xxi. (1904) pp. 297-314. J Tom. cit., pp. 384-397, pi. 1. 



§ Bot. Zeit., lxiii. (1905) pp. 51-130, pis. 4-5. 



|| Proc. Boston Soc. Nat. Hist., xxxi. (1903) pp. 211-45, pis. 11-15. 



