ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 335 



BOTANY. 



GENERAL, 



Including" the Anatomy and Physiology of Seed Plants. 



Cytology, 

 Including" Cell-Contents. 



Chromosomes in Zea Mais — Y. Kuwada {Journ, Coll. Scl. ToUo, 

 1919, 39, Art 10, 1-148, 2 pis.). A papei\dealiDg with the number and 

 individuahty of the chromosomes in Zea Mais, and with the origin of 

 this species. The author finds that the number varies from ten to 

 twenty ; plants which may be regarded as the ancestors of this species, 

 and those which are nearly related, also usually have twenty chromosomes 

 in the cells of the root-tips. In a few species of sugar-maize the number 

 of chromosomes varies with the different species ; in the root-tips ex- 

 amined they varied between twenty and twenty-four. There appears to 

 be no relation between the number of chromosomes and the chemical 

 constitution of the endosperm. Comparative examination of the number, 

 size and length of the chromosomes in the root-tip proves that increase 

 in the number is the result of transverse division of the chromosomes. 

 The dissimilarity in these respects in the component chromosomes seems 

 to confirm Collins's opinion that Z. Mais is a hybrid between Euchlwna 

 and an unknown plant belonging to the Andropogoneas. Three kinds 

 of chromosomes are characteristic of the species : — (1) Long, with a 

 tendency to divide transversely, derived from the EiichJsena ancestor ; 

 (2) shorter, with no such tendency, derived from the Andropogon 

 ancestor ; (3) chromosomes found in certain species in which the 

 transverse division has become a fixed hereditary character. The chro- 

 mosomes which split or tend to spHt are dominant to those which do not 

 split, but the dominance is an unstable factor. The different combina- 

 tions of these three kinds of chromosomes cause a variation of the 

 number within certain limits, and result in two kinds of gametes, one 

 of which is characterized by a constant number of chromosomes, and 

 another in which the number is variable. The size of the nucleus 

 and of the cell are dependent upon the size of the chromosomes, and 

 conversely the chromosomes themselves vary with the size of the cell. 



S.G. 



Crystals in Australian Timbers.— E. T. Baker {Journ. Proc. 

 Roy. Soc. JV.S. Wales, 1918, 51, 435-44, 9 pis.). The writer has 

 examined specimens of timber belonging to twenty-two families, and 

 finds that fifteen of them contained crystals in the secondary wood. 

 The crystals were so numerous and well-defined that it was possible to 

 determine their crystalline system without any special preparation or 

 breaking down of the wood. They were usually contained " in a special- 

 ized form of chambered wood-parenchyma, with partitions dividing it 



