392 SECTIONAL TRANSACTIONS.— K. 



Arthrocnemum glaucum, A. fruticosum, A. sp. n. B, A indicum, A sp. n. C, A. nom. 

 nov. D (=<S. pachystachyum Black non Bunge), A. sp. n. E, A. sp. n. F, A. sp. n. G. 

 A. sp. n. H, A. sp. n. I, A. sp. n. K, A. sp. n. L, A. comb. nov. K (=S. perenne var, 

 radicans), A. sp. n. L, Halocnemum strobilaceum, H. sp. n. M., and Halopeplis 

 amplexicaule. 



The present work supports Dr. de Fraine's main conclusion that the succulent 

 exoskeleton of the glassworts is foliar in origin. 



Details of the distribution of ' spiral cells ' and ' stereids ' in the foliar sheath, 

 and endodermis of the above species will be given. These details confirm Dr. de 

 Fraine's work in so far as the species common to western Europe and Africa are 

 concerned. 



Mr. B. R. Roux. — Growth Forms of Marsilia macrocarpa. 



Afternoon. 

 Excursion to Klipriversberg. 



Thursday, August 1. 



Presidential Address by Prof. A. C. Seward, F.R.S., on Botanical 

 Records of the Rocks. (Sec p. 199.) 



Dr. I. B. Pole Evans, C.M.G. — The Botanical Survey of South Africa. 



Prof. J. W. Bews and Mr. J. E. van dee Plank. — Response to the Resti^ig 



Season in South African Plants. 



The tropical hygrophUous element in the South African flora shows no well-marked 

 responses to seasonal variations. The temperate element of the south-west and 

 mountain regions remains, for the most part, evergreen, and there is therefore in this 

 case as well no definite period of complete rest. In the large sub-tropical element, on 

 the other hand, the dry winter resting period has undoubtedly been responsible, in a 

 general way, for the high degree of differentiation reached. WhUe the methods of 

 comparative morphology do throw considerable light on the problems involved, in 

 recent years more attention has been paid to the basic physiological processes. 



Colloidal carbohydrates (both pentosan and hexosan) increase with aridity. 

 Different sides even of the same tree may differ ■widely in chemical composition. In 

 perennials storage carbohydrates are often drawn upon to a much less extent than 

 is commonly supposed for the purpose of flower and seed production. 



The imbibition capacity and general functional significance of plant colloids in 

 connection with arid conditions and seasonal responses require further investigation. 



Prof. R. R. Gates.- — Chromosome Linkage. 



Linkages of chromosomes during the prophase of the reduction division, which 

 therefore limit the free distribution of chromosome pairs in meiosis, have now been 

 discovered in several plant genera, including Oenothera, Godetia, Rumex, Aucuba and 

 Tradescantia. 



In CEnothera, where they have been most extensively studied, they appear to be 

 clearly related to the genetic behaviour, forming the basis of much of the widespread 

 genetic linkage in OSnothera hybrids. A striking feature of these linkages is that 

 they remain constant, the Fj showing the same arrangement as the Fj. Comparison 

 of the linkage in a consideralsle number of the F, hybrids with that of the parents has 

 so far failed to disclose any general rule of relationship. The linkages in the hybrid 

 may be the same as those of either parent or may differ from both. 



In mutations the linkage is usually less than in the parent form, but in gene 

 mutations, such as CEnothera rubricalyx, there is no change in the chromosome linkages. 



It appears probable that manj^ of the wild species of Oenothera are persistent 

 species-hybrids which breed true on account of the chromosome linkage, and that 

 this is the condition under which the evolution of the genus QSnothera has taken 



