648 SUMMARY OF CUKKENT RESEARCHES RELATING TO 



it is usually considered that " hybridization aided by cultivation " is 

 the chief cause of double flowers, yet it is evident that some other 

 factor must be present, since all the above occur double in the wild 

 state. The author deems it probable that insects play a very im- 

 portant part in this matter. 



Superposed Stamens.* — Mr. T. Meehan brings forward argu- 

 ments in favour of tho view that when stamens occur opposite to the 

 petals and attached to their base, the ordinary theory of the sup- 

 pression of an intermediate whorl of stamens does not account for the 

 phenomenon so well as the hypothesis that the stamen is not in this 

 caso a metamorphosed leaf, but is a modified axial bud at the base of 

 the petal. This view is supported by a description of the structure 

 of the organs in question in Mahernia verticillata, a plant belonging 

 to the Biittncriacete. 



Composition of the Pollen of the Pine.j — Dr. A. v. Planta 

 gives tho following as the composition of the pollen of tho pine : — 

 Water, 7 ■ 66 per cent. ; N, 2 • 65 ; (N X 6 • 25, 16 • 56) ; non-nitrogenous 

 matter, 72 • 48 ; ash, 3 • 30 ; hypoxanthin and guanin, • 04 ; saccharose, 

 11-24; 6tarch, 7-06; cuticule, 21-97. By cuticule is meant the 

 chemically changed substance of the cell-wall which overlays various 

 structures and is in direct contact with the air. It is estimated by 

 digesting the pollen for three days in a 5 per cent, solution of potash in 

 alcohol, which removes the oil, &c. The residue is then boiled with 

 semi-normal hydrochloric acid for two hours, which removes the last 

 traces of starch ; other soluble matters are removed by ether, and 

 nothing but cuticle remains. 



Composition of the Ash of the Pollen of Pinns sylvestris.f — 

 MM. A. Famintzin and D. S. Przybytek find, in the pollen of Pinm 

 sylvestris, 6 ■ 79 per cent, water and 3 ■ 30 per cent. ash. The com- 

 position of the ash is as follows :— K,0, 34 ■ 95 per cent. ; N,0, 3* 62 ; 

 MgO, 6 • 99 ; CaO, • 88 ; P 2 5 , 28 • 56 ; S0 3 , 14 • 83 ; CI, • 99 ; Fe 2 O s 

 and A1 2 3 , 5 • 30 ; Mn 2 3 , a trace. The proportion of nitrogen was 

 2 - 4 per cent. By treating the pollen with a 1 per cent, solution of 

 soda, and acidulating with hydrochloric acid, a small quantity of a 

 precipitate was obtained corresponding in its reaction to nuclein. 



Heterocarpous Fruits. § — Dr. A. N. Lundstrom illustrates the 

 phenomenon of heterocarpy in fruits, especially in different species of 

 Calendula and Dimorphotheca belonging to the CompositaB. Three 

 different forms may often be found in the same species, viz. : — 



(1) anemophilous fruits, slightly curved, and with the outer pericarp 

 extended into a floating apparatus for carriage through the air; 



(2) bristle-fruits, without any wing, and with a number of stiff hairs 



* Proc. Acad. Nat. Sci. Philad., 1886. pp. 9-11 (1 fig.). 



t Landw. Versuchs-Stat., 1885, pp. 215-30. See Journ. Chem. Soc. Lond.— 

 Abstr., 1. (1886) p. 91. Cf. this Journal, ante, p. 97. 



J Bull. Acad. Imp. Sci. St. Petersbourg, xxx. (1886) pp. 357-62. Cf. this 

 Journal, ante, p. 97. 



§ Naturv. Studentsalls. Upsala (Bot. Sekt.) Nov. 3, 1885. See Bot 

 Centralbl., xxv. (1886) p. 319. 



