B00K-2S0TES, ^"£WS, ETC. 231 



BOOK-NOTES, NEWS, etc. 



At the meeting of the Linnean Society on June 19, Mr. T. A. 

 Dymes read a paper entitled *' Notes on the Life-history of the Yellow 

 Elag (Iris Pseudacorus Linn.), with special reference to the seeds and 

 seedlings during their first year," of which the following is an 

 abstract: — The xerophytic adaptations and contractile roots of the 

 plant are a protection from some of the dangers of the physical world. 

 Its acridity and astringency protect it from being readily eaten, but the 

 larvae of some insects feed upon it, those of a sawfly do considerable 

 damage ; a few molluscs resort to it for food. It appears that wild- 

 fowl eat the seeds and the very young seedlings ; it is also attacked 

 by a parasitic fungus. Its height and strong growth protect it from 

 practically all its associates. The plant hibernates and the normal 

 minimum for the seeds is about seven months, the maximum being 

 not less than twenty. It flowers in its fourth year ; the capsules 

 begin to dehisce in September. There are two kinds of seed, flat and 

 round, and the difference between them has some significance both in 

 dispersal and in germination. Uninjured seeds float for two years or 

 more. The most important of the agents are diving wild-fowl and 

 the least the wind ; running water plays a very considerable part. 

 The flat seeds are adapted to long-distance dispersal by wild-fowl and 

 to being blown short distances by the wind. The round seeds, with 

 the exception of those afloat on running water, serve to fill up the 

 death gaps at home. There are two phases of germination : — (1) 

 Internal plumular growth followed by (2) the extension of the radicle, 

 the latter requiring the higher temperature. Seeds that have sunk 

 automatically possess an internal water supply and germinate more 

 freely than the floaters. The essentials are continuous moisture 

 coupled with a high temperature. Floaters, seeds at the bottom of 

 shallow water, and those in saturated mud, succeed best : under the 

 most favourable conditions a full 40 per cent, germinate in their first 

 year. In nature the general average is probably 20 per cent. The 

 round seeds appear to germinate in the first year more slowly and to 

 yield a lower average than the flat ones. For seeds in their second 

 year the general average in nature seems to be about the same as for 

 those in their first, 20 per cent., but a good deal more evidence 

 is required. Burial of the seeds is effected by dead leaves and debris, 

 and they are also trodden into soft mud by water-birds. The chief 

 difficulty of the seedling from an unburied seed is to secure anchorage. 

 Frost and air-bubbles lift or uproot the young seedlings. The 

 floaters, which when borne afloat can be distinguished from the mud 

 seedlings by the root sj'stem, are exposed to great dangers ; when 

 together or in debris the}' erect themselves, but unless they drift on 

 to mud or into the shallows either before or after erection they are 

 doomed to death. The height to which seedlings attain during their 

 first year varies from two inches for the flat-floater to thirteen for 

 those in mud from first-year seeds and 19| inches from seeds in their 

 second year. The seedlings perish in inconceivably great multitudes, 

 and probably the vast majority of the floaters are a dead loss to the 

 species. 



