SECTIONAL TRANSACTIONS.— K. 615 



Friday, September 7. 



Dr. J. BuRTT Davy. — Observations on the Forest Flora of Northern 

 Rhodesia. 



Mr. J. Walton and Mr. R. Koopmans. — The Preparation of Cellulose 

 Films and their use in making Serial Sections of Coal Ball Plants. 



Miss E. S. DowDiNG. — The Sand-hill Areas of Central Alberta. 



Illustration will be given of the distribution of the main sand-hill deposits of 

 Alberta, and the sand-hills of the central area will be considered in detail. These 

 hills were originally washed out from terminal moraines, so that they mark the 

 positions of old drainage courses. The vegetation of such areas is one of sharp 

 extremes depending on the varying water content of the soil. The swamps, bogs 

 and heaths of the sand-hills will be described and reference made to the distribution of 

 the Pine Mistletoe on the hill summits. Some account will also be given of an 

 expedition to the sand-dunes in Jasper National Park, and of the origin and stabilisa- 

 tion of the dunes. 



Dr. K. B. Blackburn. — Chromosomes in some Species of the CaryophyllacecB. 



Differences in chromosome number, including polyploidy, which occur both 

 within a species and between species will be discussed. The variety of chromosome- 

 form within the group will also be considered. 



Dr. E. M. HiGGiNS. — Types of Reduction division in Stypocaulon and 

 Cladophora. 



Stypocaulon scoparium, Kutz. In view of the recent work on Pylaiella, Ectocarpus 

 and Sphacelaria, an investigation of the cytology of Stypocaulon scoparium, Kutz., 

 has been undertaken with special reference to the unilocular sporangia. The diploid 

 chromosome number of 32, as found by Escoyez, has been connrmed. 



In the division of the enlarged unilocular sporangial mother-tell, the phenomena 

 of synapsis are clearly shown. The prophase is prolonged, and further stages in the 

 heterotype division have not yet been found. But the reduction of the chromosomes 

 is clearly shown to have taken place throughout all the subsequent divisions in the 

 unilocular sporangia, in which 16 chromosomes have been counted. 



Cladophora sp. All stages in division of the diploid nuclei have been studied, and 

 the chromosome number is 24. No continuous spireme is found in the prophase 

 stages, and the individual chromosomes are early differentiated. 



In the terminal parts of the filaments, the phenomena of reduction division are 

 manifest, the diakinesis stage being especially marked. In the anaphase of the 

 heterotype division the 12 chromosomes, on moving to the poles, frequently show 

 themselves to be split in readiness for the next division. One homotypic division, 

 showing clearly the reduced number of chromosomes, follows the heterotype division 

 and precedes the differentiation of the spores. 



Dr. M. Knight. — Sexuality in the Ectocarpaeece. 



The discrepancy in behaviour recorded by various workers for the zoids emergent 

 from the plurilocular sporangia of Ectocarpus siUculosus growing in northern waters 

 as compared with those from plants growing in Mediterranean regions has been 

 investigated. It is found to rest upon a cytological basis. It has been established 

 that, in one and the same species in widely separated geographica Iregions, two distinct 

 types of life-history exist, in one of which the haploid and in the other the diploid 

 stage is the dominant. The subordinant stage shows either restricted development 

 or reduction to a single cell stage. 



The relationship of the unilocular and plurilocular sporangia in these two cases is 

 then discussed. Cytological distinction is found to be associated with complete 

 morphological similarity. 



