H. BOTANY AND HORTICULTURE. 353 



vertical and horizontal parts also gradually disappears, and 

 the awn becomes straight ; (2) as the awn becomes dry again, 

 the movements just described are reversed, the angular bend 

 and the torsion of the lower part of the awn appearing. 

 What special advantage it may be to a plant that its seeds 

 should be buried is uncertain ; in the case of Stipa, at least, 

 it seems to have no connection with germination ; it is con- 

 jectured that it may serve as a protection against graminiv- 

 orous birds, etc. JVcituralist, Jwie, 1876. 



DOES THE AGE OF A TREE INFLUENCE THE TIME OF LEAFING ? 



M. Alph. de CandoUe caused observations to be made in 

 the botanical gardens of Paris and Pisa to settle this point. 

 Unfortunately, however, the results w^ere negative. M. De 

 Candolle refers to one case in which the date of coming into 

 leaf of a horse-chestnut tree has been carefully recorded for 

 sixty-eight years, and another for fifty-seven years; both at 

 Geneva. Of course any differences due to age would be 

 small in comparison with those due to climate, yet they might 

 be expected to be sensible in the long series of years if age 

 really made any difference. But the figures do not bring to 

 view any tendency to either earlier or later leafing with the ad- 

 vance of years. Archives des Sciences de la Bibl. Universelle. 



FLOATING SEEDS. 



There is a considerable number of seeds with a specific grav- 

 ity less than that of water, some as low as 0.75. Van Tieghem 

 finds that this is due to difterent causes. More commonly 

 the seed owes its lightness to its coats, either by a separation 

 between the two in drying, or between the inner and the ker- 

 nel, leaving an air-space, or by a loose cellular structure of 

 the coat. Sometimes, as in castor-oil seeds, the integument 

 is heavier than water, but the kernel is so much lighter as to 

 float the seed. This comes from a separation of the two co- 

 tyledons during the natural desiccation, leaving a consider- 

 able cavity filled with air. American Journcd of Science. 



EAPID GERMINATION. 



Most gardeners have either heard or read of, if not seen, 

 the singular rose of Jericho, ^nas^a^^m hierochimtina. The 

 plant belongs to the Crucifera?, and is a dwarf radiately 



