ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 457 



grain. He finds that the percentage of proteid nitrogen increases as 

 ripening proceeds, but that nitrogeu in other forms, especially aspara- 

 gin, diminishes. In wheat and rye the percentage of total nitrogen 

 diminishes, but increases in oats and barley. 



Changes during Ripening of Apples.* — R. Otto finds that the per- 

 centage of water increases during ripening. The starch diminished 

 from about 4 p.c. (Sept. 7) to 1*6 (Oct. 5), and disappeared entirely 

 when the fruit was stored ; the ash decreased, whilst the cellulose re- 

 mained constant. There was an increase in nitrogen during ripening 

 on the trees, but afterwards a decrease. 



Composition of Proteids and Cell-Membranes in Bacteria and 

 Fungi.f — K. S. Iwanoff finds tbe proteids to be nuclei-proteids con- 

 taining in bacteria 16 -3 p.c. nitrogen and 1*8-2-2 p.c. phosphorus, in 

 fungi 15* 1—16 ■ 2 p.c. nitrogen and 0*7-1 p.c. phosphorus. Tbe autlmr 

 also confirms the existence in the cell-membranes of cbitin apparently 

 identical with animal chitin. 



Proteid Formation in Plants.} — F. Czapek emphasises the import- 

 ance of amino-compounds in the synthesis of proteids in plants. 



General. 



Colours of Northern Polypetalous Flowers.§ — J. H. Lovell con- 

 tinues his studies on the colours of flowers. He finds that throughout 

 the Choripetalae conspicuousness is generally correlated with insect 

 fertilisation. In many genera tbe species can be arranged in a pro- 

 gressive series showing an advance from inconspicuoueness, few visitors, 

 and self-fertilisation to many visitors, great conspicuousness, and loss of 

 power of self-fertilisation. While green flowers are small and frequently 

 apetalous, white and yellow vary from small to large, are most common, 

 and contrast more strongly with the foliage than purple or blue. Of the 

 71 polypetalous families, 43 contain white, 41 yellow and 29 both kinds 

 of flowers. White flowers are most common in families or genera con- 

 taining shrubs and trees, in tbe case of small flowers aggregated in a 

 dense inflorescence and in nocturnal flowers. Yellow flowers are more 

 commonly associated with a herbaceous habit, and are most abundant in 

 the same families as white flowers, unless the species are shrubs or trees. 



There is no evidence of the preference of beetles for flowers of any 

 particular colour. They are most common in connection with small 

 white clustered flowers with easily accessible pollen and honey. Diptera 

 visit most frequently white and yellow flowers, but as they become more 

 specialised and restrict themselves to flowers the percentage of visits to 

 red and blue flowers increases. They appear to find a particoloured or 

 dotted inflorescence, as in Cruciferae and Saxifragaceae, attractive. Car- 

 rion flies prefer maladorous, lurid purple or flesh-coloured flowers. The 

 changes of colour and their sequence in individual flowers are note- 

 worthy. Green changes to white, yellow, red, purple, or violet ; white 

 to green, yellow, red, or blue; yellow to white, red, or blue; red to blue. 



* Bied. Centr., xxxi. (1902) pp. 107-8. See Jouru. Chem. Soc, I.e. 

 t Beitr. Chem. Physiol. Path., 1902, pp. 524-37. See Journ. Chem. Soc., 1. c. 

 p. 279. X Tom. cit., pp. 538-00. 



§ Amer. Nat., xxxvi. (1902) pp. 203-42. 

 August 20th, 1902 2 h 



