SECTIONAL TRANSACTIONS.— K. 617 



. controlling the mutation seems to vary in strength at different periods in the 

 development of the plant. The relationship of this phenomenon to somatic 

 segregation is of interest. 



Prof. W. Robinson and Miss P. M. Skrine. — The Growth and Propagation 

 of some Salt Marsh Fuci. 



The forms dealt with are the ecads muscoides (Cotton), ccespilosus (Baker and 

 Bohliug) and volubilis (Turner) of Fucus vesiculosxis . Individuals of the first two of 

 these ecads may be arranged as a continuous series varying in size and form according 

 to their habitat, but ecad volubilis differs from these and may prove to be an ecad 

 of Fucus spiralis (L.) (F. platycarpus, Thur.). 



These ecads are being cultivated successfully in aerated sea-water either with or 

 without the addition of a nutrient solution of salts. Under the cultural conditions 

 the cyHndrical ecad muscoides has become flattened and has taken on the appearance 

 of ecad coespitosus. 



In nature the three forms are found to grow in substrata of different Vh values, 

 and the experimental work in progress may indicate whether this or more direct 

 nutritional factors determine the morphological differences observed. 



As has previously been recorded, the three ecads reproduce vegetatively by means 

 of proliferated branches. The present work has, however, indicated that there are 

 striking differences in the origin and development of the proliferating growths in the 

 different ecads. It is found that the proliferations from ecad volubilis are always 

 developed from hair-pits. The branches are produced either singly or in small numbers 

 from the hair-pits, which are found on the margin and on the surface of the thallus. 

 They take their origin in a group of hairs of the hair-pit and develop by the congenital 

 growth of these hairs. An apical cell of the branch is differentiated later, and this 

 continues the growth of the branch. 



The origin of the proliferations in the ecads muscoides and ccespitosus shows no 

 relation to the hair-pits, and in this respect their manner of origin may be compared 

 with that of the proliferations in wounded specimens of a typical Fucus vesiculosus. 



Suggestions are offered as to the bearing of the origin and development of the 

 proliferating branches, which arise in hair-pits, on the morphology of the hair- pit, and 

 on the more general relations of this to apical development in the Fucacece. 



Dr. R. M. Buchanan. — The Decay of Stone in Buildings and Monuments : 



a Biological Problem. 



The decay of stone in buildings and monuments presents a problem of importance 

 to the country on account of the structural damage which it produces and the costly 

 measures which are required to make good its ravages. The process has for long 

 been one of interest to physicists, chemists, architects and craftsmen, and has hitherto 

 been regarded as due to the solvent action of adventitious gases in the atmosphere 

 arising from the combustion of coal or emanating from chemical works. Another 

 aspect of the problem presented itself a considerable time ago when the decay was 

 discovered to present some features characteristic of an infective process. The 

 condition in many respects simulated the progress of a disease and appeared in conse- 

 quence to justify the designation Lupus lapidis. The localisation and distribution 

 of the decay and its prevalence in buildings far removed from the influence of smoke 

 or other atmospheric pollution lent support to this view. Cultural experiments were 

 accordingly undertaken, and micro-organisms were found abundantl.y in material 

 from the decaying surfaces, the organisms evidently finding the conditions necessary 

 and natural for their growth (reported on in a paper read before the Royal Philosophical 

 Society, Glasgow, November 4, 1904). These earlier cultural tests have been repeated 

 many times in recent years from buildings in different localities with confirmatory 

 results, a distinctive flora tending to appear in each type of decay. Three kinds of 

 organisms — bacilli, yeasts and moulds — were almost always to be found separately 

 or in association in the decaying surface. Attention was specially directed to the 

 investigation of a few of the species which constantly made their appearance in 

 cultures, and which by their production of carbonic acid and sulphuretted hydrogen 

 might justifiably be regarded as concerned in the process of disintegration affecting 

 the stone-work. The operation of biological factors would thus appear to be essential 

 in the process of stone decay in buildings. 



