458 SUMMARY OF CURRENT RESEARCHES RELATING TO 



of the surrounding solution and apparently also of the nature of the 

 solution. Once taken up it is retained for some time. 



Acid Excretion of Roots and Fungi.* — Gustav Kunze finds that 

 the roots of higher plants do not excrete mineral acids ; that the solvent 

 action of the soil is due to organic acids alone, and as the amount of 

 acid in many plants is infinitesimal, the plant relies on mycorhiza for the 

 desired effect. By cultures of roots and hyphse on marble he found that 

 the latter had pierced deeper into the stone ; he found also that humic 

 acid played only a small part in the corrosion of minerals as compared 

 with fungus hyphse. He examined further the action of lichens on 

 rocks. Among granite lichens it was discovered that the mica con- 

 stituent suffered least from hyphte. By growing Penicillium on litmus 

 paper soaked in a nutrient solution he was able to determine the 

 abundance of the acid, and that it was oxalic acid. Plant roots grown 

 in the same conditions gave only a slight acid reaction on the paper. 

 Hence he concludes the enormous importance of fungus hyphse to the 

 higher plants. 



General. 



Colour as an Attraction for Bees.f — GL Bonnier has experimented 

 with bees for the purpose of testing whether the colour of flowers is the 

 source of attraction. The author considers that previous workers have 

 not given sufficient consideration to the social organisation of bees. He 

 finds that among the workers leaving the hive are some which seek for 

 honey, etc., and then point it out to the rest of the colony. These 

 seekers are very numerous in the early morning, but later on they 

 become plunderers. If honey, placed on variously coloured cards, is 

 set near the hives in early morning, the seekers soon discover it ; if it is 

 later, when the seekers are less numerous, the plunderers will continue 

 their appointed tasks, and the honey will remain untouched for a long 

 time. These results are independent of the colour of the cards. All 

 experiments tend to show that when bees have taken up their work for 

 the day, they are usually unaffected by honey, etc., even if placed on 

 conspicuously coloured flowers or cards in the vicinity of their labours. 



CRYPTOGAMS. 



Pteridophyta. 

 (By A. Gepp, M.A., F.L.S.) 



Botrychium Lunaria.:}: — H. Bruchmann gives detailed observations 

 on the prothallium and sporophyte of Botrychium Lunaria. Whereas 

 Ophioglossum vulgatum is propagated by numerous suckers, this method 

 of growth is lacking in B. Lunaria : every sporophyte is the direct pro- 

 duct of a gametophyte. Hence the minute prothallia must be sought 

 with a lens beneath the surface where a sporophyte has lately shed its 

 spores ; it is useless to search beneath young plantlets, for these have 



* Jahrb. wiss. Bot., xlii. (1906) pp. 357-93. 

 T Comptes Rendus, cxli. (1906) pp. 988-94. 

 % Flora, xcvi. (1906) pp. 203-30 (2 pis.). 



