320 SUMMARY OF CURRENT RESEARCHES RELATING TO 



tions of disodic phosphate, and that no concentration of the solution 

 will produce a negative curve. Stronger solutions (1*5 p.c.) cause first 

 a curving toward the salt and then death. The death of the roots may 

 he due to the osmotic strength of the surrounding medium. The 

 particular attractive component of the salt was not determined ; it may 

 be either the sodium or the phosphoric acid ion ; the work of Stange 

 and Buller suggests that the P0 4 ion is the active one. Roots of 

 Cucurbita Pepo are indifferent towards chemicals, a fact which suggests 

 that sensitiveness to chemicals may vary in the same way as sensitive- 

 ness to light ; that is to say, roots may be either chemotropic or non- 

 chemotropic. None of the roots tested gave any indication of osmo- 

 tropism ; the experiments suggested that osmotropism and hydrotropism 

 are not identical. 



General. 



Endophytic Fungus of Orchids.* — Noel Bernard, continuing his 

 investigations on this subject, has endeavoured to cultivate the endo- 

 phytic organisms of different Orchids. He finds in the case of a hybrid 

 Cyprlpedium, that the fungus, a hyphomycete morphologically identical 

 with that previously isolated from seedlings of Cattleya, penetrates the 

 embryo always at the pole turned towards the micropyle. The large 

 fleshy roots of Spiranthes autumnalis yielded a hyphomycete indistin- 

 guishable from the preceding. The results of experiment suggest that 

 the same endophyte can impregnate different Orchids ; that is to say, 

 we are dealing, as in the case of the Rhizobium of the Leguminosge, 

 with a parasite characteristic of the family. 



Mechanics of Seed-dispersion in Ricinus communis.! — J. B. 

 Dandeno finds that as the carpels begin to separate in the ripe fruit, 

 one of the three is so placed that the angle of projection of the seed is 

 that which gives theoretically the greatest range ; the other two carpels 

 are in a less favourable position. The fruit splits septicidally from the 

 base till a point is reached about 3 mm. from the apex, and meanwhile 

 the carpels also separate from the central column, which bears three 

 projecting processes upon which they are finally suspended. The carpel 

 with its dorsal side uppermost has the most sun exposure and dries 

 most quickly ; this is also the one which has the best position for pro- 

 jection. After the carpels are entirely free from the central column, 

 the contraction of the dorsal wall continues until the carpel gives way 

 at its weakest point. This is at the apical end, where are three pairs 

 of tooth-shaped arrangements meeting at a line about 3 or 4 mm. long. 

 Each carpel splits apart at this line with some violence ; this acts as a 

 spring suddenly relaxed, and the carpel is projected ; the seed, though 

 projected with the carpel, is at this time or soon after, released. 



As the result of a calculation the writer finds that the ground 

 covered by the seedlings from a single plant would be approximately 

 105 acres in 100 years. This calculation is based upon the considera- 

 tion of the fruit as a projectile alone, and takes no account of other 



* Compti'S Rendus, cxxxviii. (1904) pp. 828-30. 

 f Bull. Torrey Bot. Club, xxxi. (1904) pp. 89-92. 



