ttJJNBAN SOCIETY OP LONDON. 59 



ABSTllACTS. 



Notes on the Li t'e-lii story of Irk Fsciuhicoras, Linn., witli s[)t'cial 



refereuce to its Seeds ;uid Seedlings. (With 1 text-tigiire.; 



By Thomas Alfked Dimes, i'\L S. 



[Read lOili June, 1919.] 



On 3Uth November, 1910, I conuauuicated to the »Society a note 

 on tlie seed of Iris Psettdacorns, Linn., in w liich I drew attention 

 to its germination while still afloat, and the dilliculty 1 had 

 experienced in raising seedlings in the open, either on or in mud. 

 On 1st November, 1917, Lt.-Col. J. H. Tull Walsh, I.M.8., 

 F.L.S., communicated the results of his experimeuts, and exhibited 

 liealthy seedlings raised from seeds on or in mud in the open. 

 In 191 S I made a great many experiments to discover why I had 

 failed. That failure was due to too low a temperature, for I 

 kept my mud sowings in cool shade, whereas a comparatively high 

 temperature is necessary for the successful germinatiou of the 

 seeds during their first season. The present cotiimunication sum- 

 marises very briefly the results of these and earlier experiments 

 and observations from 1913 onwards. I need only add that iu 

 favourable years, of which 1918 was one, the temperature of the 

 nuid and shallows, in which the seeds of this species gern)inate 

 normally in xMay and June, frequently rises many degrees above 

 70° 1\ during the day, without falling appreciably below it during 

 the night, and for a period sullicieutly long to ensure successful 

 germination ; that in my cool shade experiments it was generally 

 nearer (30° ¥., that it never rose as high as 65° F., and that not a 

 single seed produced a seedling, whereas in the higher temperature 

 I was at the same time recording very satisfactory results from a 

 large number of separate sowings under various conditions. 



Iris Faeadacorus, Linn., is distributed in abundance thronghonfc 

 the British Isles, ascending from sea-level to about 700 feet. Its 

 xerophytic adaptations protect it from some of the dangers of its 

 envii'onment. Protection from animals is afforded by its acrid 

 and astringent secretions, but it is attacked by the larvae of 

 various insects and molluscs. Domestic ducks eat the seeds and 

 the very young seedlings, and it is almost certain that wild-fowl 

 do so too. Puccinia Iridis, DC, is recorded as a fungal foe, and 

 floating seedlings which have failed to strike root sink in the 

 autumn and perish from disease during the winter. An immense 

 amount of observation on the natural enemies has, however, still 

 to be made and is very much to be desired. 



In some years, when February is hot and sunny, germination 

 commences in that month, but in others, when the season is cold 

 and dull, not until mid-June ; the normal minimum period in 

 nature, commencing in September, when the capsules begin to 

 dehisce, is therefore from five to nine months, according to the 

 season, and usually about seven ; the maximum is certainly not 



