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Transactions of the Society. 



pressed, and gradually becoming very turgescent. This is not the 

 case with the outer layer. Finally, the coat splits down one side, 

 the inner cells expand at once, thus turning the coat inside out, 

 the inner and now larger layer coming to the outside, while the 

 originally outer layer is turned inwards. The result of this is that 

 the seed is jerked out to a considerable distance. Owing to the 

 elevation of the capsule, the seeds fly clear of the leaves. 



Lastly, in the Balsam {Impatiens), the dividing walls of the 

 5-chambered capsule are thin, and eventually separate themselves 

 from the centre, which thus becomes a pillar standing in the middle 

 of the fruit. As the fruit dries, the cells immediately below the 

 epidermis are in a state of gradually increasing tension, more so 

 than the layers below. Moreover, while the carpels of Geranium 



straight, and thus 



position like that of a watch-spring, 

 those of Impatiens turn slightly to 

 one side (the right), the result of 

 which is that in contracting they 

 resemble a corkscrew. Finally, 

 the fruit bursts, the valves roll up 

 suddenly like a watch-spring, and 

 fly off, carrying the seeds with 

 them. In this case, therefore, the 

 elastic tissue is part of the ovary 

 — not, as in the preceding genus, 

 the outer coating of the seed 

 itself.* 



Acerace.e. — The Maples (Acer- 

 aceae) are trees, and have winged 

 fruits, which are often carried by 

 the wind to a considerable distance. 

 PcHAMNACE.e. — Our British spe- 

 cies of this family (the Buckthorns) 

 are also shrubs or small trees, and 

 the fruit, as is so often the case 

 with small trees, is a berry. The colour is black or dark purple. 



Lkguminos.e. — The ovary of the Peaflower is single 1-celled, 

 with one or more seeds arranged along the inner or upper angle. 

 The fruit is a pod. The seeds as a rule are smooth. 



With this uniformity, however, is combined much variety. In 

 some ( Vicia hirsuta, Genista anglica, G. tinctoria, TJlex, Ononis, 

 Lotus, Lathyrus Nissolia, L. pratensis, L. maritimus) the pod bursts 

 open elastically and scatters the seeds. Each valve of the pod 



Fig. 73.— 1, Pod of Common Vetch. 

 The line ab shows the direction 

 of the woody fibres. 2, Pod of 

 Common Vetch after bursting 

 open. 



* Zimmerman explained the dehiscence by the tension of the woody layer ; 

 Steinbrinck, by the difference between the tension of the woody layer and of the 

 outer epidermis, which is also Eichholz' view. (Pringsheim's Jahr. Wiss. Bot. 

 xvii., 1886.) 



