Soo 



turgidity, 

 the part i 



their t- 



()i;c 111 



:ui(l . 

 thalli 



Iriii I 



frequently 

 unfavoural 

 usualh tlM 



NATURE 



[August 25, 1923 



.squamoM 



)lc for tl 



I 110 (Icliniilal i< 



in length and number, loosen 

 utually incorjxjrate them in 

 !'! ioiis, always microscopic, 

 thalli below the ajjothecia 

 '• rhizoids of the foliaccous 

 the thalhis of a Pertusaria 

 Microns iiulusions through- 

 Ill tln-ir- Ihn kiic-, ., 

 it tin- kI.i-'i 1^ the one IlKi^t 

 I 111- ( iMh lit HHi-^ liiTc are iiu^st 

 I lc\ cliiiimciit of lichens and 



til 



tlialliis. The 



Yn,. 3. (X36.) 



{(i) riiTccdiiii't inu'oruin DC. and circular pit; 

 {h) corrosion shouini; outlines of original pits. 



lichen constituents, hyphae and gonidiae, are not 

 associated in a definite tissue but exist as a thin 

 layer, resembling a cobweb, over more or less the 

 whole surface, which shows a similar extensiveness 

 in its alteration. Hyphae and gonidiae pass between 

 the scales of glass, the former the more deeply, and 

 incorporation follows. 



The lichen flora of church windows is practically 

 confined to the exterior, and necessarily limited by 

 the exposed and slippery substratum. Twenty-three 

 species and varieties have been identified, including 

 only one fructaceous, Ramalina polymorpha Ach. 

 var. ligulata Ach., and two foliaceous, X author ia 

 parietina Ach. and its variety ttimida Wed. All 

 the others are crustaceous, these' being the best 

 adapted to the environment. There appears to be 

 a succession in the flora analogous to that on a 

 larger scale of the flora of dunes in so far as there is 

 a preparation of the substratum for subsequent 

 species of lichens. A crustaceous species, Diploicia 

 canescens Ach., is the most abundant but it rarely 

 occurs except on the unaltered glass ; its thallus, 

 of a maximum diameter of 4-6 cm., disappears and 

 leaves a slightly roughened surface. Other crusta- 

 ceous species follow, two varieties of Placodium 

 murorum DC. being most interesting, showing as 

 they do a conformity between their disc-shaped 

 thalli and the circular pits of their substratum 

 (Fig. 3). The crustaceous lichens apparently cease 

 to thrive once the glass becomes deeply corroded, 

 yet it is on this considerably altered surface that 

 the fructaceous and foliaceous species exist (Fig. 4). 



The lichens are not well developed. Some are 

 not visible to the naked eye ; the thallus is small, 

 mal-formed, incomplete, or greatly soredified ; apo- 

 thecia are frequently absent or, conversely, persist 

 longer than the thallus. Their determination is 



difficult, and is often only possible through a pro 

 longed and concentrated stuay of the gradual chaii^«- 

 unficrgone by a s| 



Lichens need j nd a ccrt 



with little wind i.. , ,.,. .aeir free gi./vM,, , ,.„.- 



secjuently, windows with a .south aspect in the 

 country and all windows in a crowd<'l i..M..iii.<..iri.,.<w! 

 arc iiiif lAoiirable substrata; they i 

 "r none at all, and sliow little <!■ 

 uMilows ui' north asi>ect, m humid, 



^iihn, l)nt ai, -^'s, lirhrns multiply abun- 



dantly and quickly, a corre- 



spondingly high dcM .,e colour 



or chen ' imposition of the glmas probably 

 influence - velopment of lichens, as it is not 



unusual 10 sec glass of cHie colour bearing many of 

 these small plants ulule adjacent glass of another 

 colour is free. 



Growth of lichens on wiii'io\s> can be prevented 

 by the simple means of regularly brushing and 

 washing the windows, or bv the application of a 

 liquid mastic to exclude air and lichen spores. The 

 essential condition for the ultimate preservation of 

 the windows is that the leadings should receive 

 constant attention and periodic renewal. 



The material examined has in the bulk been 

 collected by M. Gaudin throughout Brittany, Nor- 

 mandy, Champagne, Ile-de-France, etc. A certain 

 number of specimens from the .^iayenne churches 

 submitted by M. Alleaume, ptuite-verrier of Laval, 

 are now deposited in the museum of that town. 



Kl(-.. 4- (<2.) 

 (.z) ('ircular jnt : (b) irregular channel ; (<-) corroded border of glass 



originally inserted in leadings; (</) transparent surl'are : r,1 li.hpn dehris ; 

 (y; Xanthoria fiariitina Ach. ; {g) Fiacodr 



Mellor, E. — Notes sur les Lichen vitrico: ptes 



rendus de la SociHS Biologique de Fra,,^^, i.,ii. 



Les Lichens vitricoles et leur action mecanique 

 sur les vitraux d'eglise : Comptes rendus, 

 Acadimie des Sciences, t. 173, 28 novembre 

 1921. 



These — Les Lichens vitricoles et la deteriora- 

 tion des vitraux d'eglise : Paris 1922. 



Summary of Thesis : Revue ginerale de Bota- 

 viqtie, Paris 1922. 

 Mellor, E. and Virville, Ad. Davy de. — La De- 

 terioration des vitraux d'eglise de la Mavenne 

 par les Lichens : Bulletin de Mayen) ' ces, 

 1922. 



NO. 2808, VOL. I 12] 



