RECENT ADVANCES IN SCIENCE 223 



doubleness in the flowers of Meconopsis, Allhcea and Dianthus 

 (Journal of Genetics, 191 7), in all of which the double condition 

 is exhibited in various degrees, so that every stage, from 

 a single to a completely double flower, can be obtained. In 

 Meconopsis the doubleness results from varying degrees of 

 petalody of the andrcecium and gyncecium, extreme forms 

 being completely sterile. Both doubles and singles breed 

 true. The former behave as dominants and the latter as 

 recessives. In Althcea the offspring which result from crossing 

 high grade doubles with singles are low grade doubles con- 

 stituting a heterozygous race. The F2 generation yields three 

 types in the proportions of one high-grade double, two hetero- 

 zygous low-grade doubles, and one single. In the genus Dian- 

 thus the author has experimented upon the Carnation and the 

 Sweet William. In the former the double type is dominant, 

 whilst in the latter it is the single type which is dominant. 

 The flowers of the Sweet William appear to present two kinds 

 of double flowers. In the one this condition is the result of 

 petalody alone, and such flowers exhibit fifteen petals, of which 

 ten replace the stamens. The second type is the outcome 

 of petalody combined with splitting, and as a consequence 

 twenty or more petals are often present. 



General. — Dr. Boycott (The Naturalist, Jan. and Feb., 191 7) 

 has investigated the occurrence of manganese in various land 

 and fresh water snails, and incidentally gives some interesting 

 data as to the amount present in various plants upon which 

 the snails feed. These show in general a very much higher 

 manganese content for water plants than land plants. The 

 quantities given are in parts per 10,000 of dried material. 

 Marrow and ash leaves gave only 0*2, grass o'6 — i*i, whilst 

 beech leaves contained as much as 8'6-io'7. Jadin and 

 Anstruc (Comptes Rendus, 19 12) in 80 species belonging to 

 32 families found from o*oi4-7'6. In most of the aquatics 

 examined, the manganese content was much higher and ranged 

 from 1 part per 10,000 in Potamogeton crispus to yy in the 

 Water Buttercup. Algal slime gave from 20 to 377, whilst an 

 aquatic moss yielded as much as 690. The manganese content 

 of various Agarics ranged from o'2 to 07. 



In 1 9 14 Prof. Bottomley described some experiments which 

 indicated that when peat is decomposed, by incubation with a 

 mixed culture of aerobic soil organisms, certain substances 



