SECT. II. SEEDS. 



it will immediately burst open, while the valves, 

 coiling themselves up in a spiral form and springing 

 from the stem, discharge the contained seeds and 

 scatter them all around. 



The bursting of the pericarp of some species of 

 Pines is also worthy of notice. The pericarp, 

 which is a cone, remains on the tree till the sum- 

 mer succeeding that on which it was produced, the 

 scales being still closed. But when the hot weather 

 has commenced and continued for some time, so as 

 to dry the cone thoroughly, the scales open of their 

 own accord with a sudden jerk, ejecting the con- 

 tained seeds : and if a number of them happens to 

 burst together, which is often the case, the noise is 

 such as to be heard at some considerable distance. 

 This crackling noise was observed and traced to a 

 fir-tree, namely Pinus Pinea, at tiendlesham Par- 

 sonage, on July 14th, 1808, by two young gentle- 

 men, my pupils, who thought the tree was bewitched 

 till the cause of the noise was pointed out to them. 



The twisted awn of Avena jatua, or Wild Oat, By the 

 as well as that particularly of Geranium cicutarium, 

 and some others, seems to have been intended for 

 the purpose of aiding the further dispersion of the 

 seed, after being discharged from the plant or peri- 

 carp. This spiral awn or spring, which is beset with 

 a multitude of fine and minute hairs, possesses the 

 property of contracting by means of drought, and of 

 expanding by means of moisture. Hence it remains 

 of necessity in a perpetual state of contraction or 

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