SECTIONAL TRANSACTIONS.— K. 4'9 



A Karyo-systematic study, which has not hitherto been made, was under- 

 taken and results so far available point to the following conclusions : 



i. The basic number of chromosomes for the tribe is 5 and not 12 as 

 was supposed by Avdulov. 



2. While a certain section, viz. Zizaniae, retained the original basic 

 number, as in two species of Zizania (zn = 30) and Lygeum spartum 

 (zn = 40), another section, viz. Oryzineae, which includes Rice, developed 

 a secondary basic number 12 through secondary polyploidy, as in the several 

 species of Rice (zn = 24 and 48) and two species of Leersia (zn = 48). 



3. The monotypic genus Lygeum, which has altogether a different habit 

 and distribution, differs from the rest of the tribe in having larger chromo- 

 somes. 



4. Both alio- and autopolyploidy appear to have played a part in the 

 differentiation of species and genera. While Lygeum spartum appears to 

 be an autopolyploid, certain species of Oryza are likely to have been derived 

 through allopolyploidy. 



Detailed studies, comprising other genera as well, are in hand. 



Mr. C. E. Ford. — Chromosome studies in the Malvaceae (3.30). 



Chromosome numbers of some thirty species are reported. These 

 support the view that the numbers 5 and 7 are basic for the family. In 

 Malva all the species examined are polyploids on a basis of 7, whereas in 

 the closely allied Lavatera aneuploid numbers also occur. There is a wide 

 range of haploid numbers in the genus Hibiscus such as n = 19, 33, C65 and 

 C72. Diploid and tetraploid races have been found in the two cultivated 

 species, H. esculentus and H. cannabinus. In Abutilon the species fall into 

 two groups, one with 7, and the other with 8 as the basic number. 



Chiasma frequencies at metaphase ranging from 1 • 26 to 1-72 per bivalent 

 were determined in Abutilon graveolens, Anoda cristata, Sidalcea oregona 

 and Sidalcea Candida. The terminalisation coefficient was approximately 

 equal in the first three species at 0-85, but in S. Candida it dropped to 0-67. 



A connection between one bivalent and the nucleolus is clearly visible 

 at diakinesis in Sidalcea oregona and at prophase of mitosis in Thespesia 

 lampas. 



In all species examined, prochromosomes were present in the resting 

 nuclei of root-tips. They were also observed in tetrad nuclei and in the 

 nuclei of anther wall cells. 



Dr. T. Swarbrick. — Relationships of scion and rootstock in fruit trees 

 (3-55)- 



It has already been established that clonal vegetatively raised rootstocks 

 influence tree size and precocity. Recent experiments have been carried 

 out at Long Ashton whereby trees have been raised which have a 

 common absorbing root system but which have intermediate stem pieces of 

 the three rootstocks MIX, II and XIII. These three rootstocks, when 

 used in the normal manner to provide a complete absorbing root system, 

 produce trees which, as regards vigour, are dwarf, semi-vigorous and vigorous 

 respectively. These experiments show that the effects produced in the 

 scion variety are almost similar in every respect, when an intermediate 

 stem piece of 9 inches long of these three rootstocks, and when the rootstocks 

 are used in the normal manner. Quantitative data are presented in 

 support of the above effect upon tree size and root development. Quan- 

 titative effects upon foliage and habit of tree growth are described. The 

 three intermediate stem pieces of MIX, II and XIII show marked differences 



