xix] INDEHISCENT FRUITS 241 



water at Roslyn Pits, Ely, on October i, 19 14. At this stage 

 the seeds were unripe and white. The fruits were brought to 

 the laboratory and kept in water. After a considerable time 

 the pericarp split irregularly, after a fashion closely recalling 

 Nymphaea\ by November 24, the fruits were in this bursting 

 condition and the seeds, which, had darkened in colour, had all 

 the appearance of being ripe. The embryos are said to be pro- 

 tected by the cuticularised epidermis of the testa^. The seeds 

 are flat and ciliated at the edge (Fig. 156 C). That these hairs 

 serve for flotation is indicated by the fact that if they are cut off 

 the least touch makes the seeds sink^. It has also been ascer- 

 tained that the seeds may become firmly attached to the downy 

 plumage of a bird's breast, by means of this fringe of hairs^. 

 The splitting of the ovary wall takes place mostly near the base 

 the lobes that are thus produced curving up until the outer 

 epidermis of the pericarp, which was originally convex, becomes 

 concave. This curvature is due to decay and loss of tissue on the 

 inner surface of the fruit-wall, followed by swelling of the rest 

 of the tissues, with the exception of the outer epidermis and 

 adjacent layers (Fig. i ^"j A and 5, p. 242). 



The fruits of Stratiotes aloides and Hydrocharis Morsus-ranae 

 are said to be burst open by the swelling of mucilage produced 

 from the testa of the enclosed seeds. 



A remarkably large proportion of aquatics, on the other hand, 

 have fruits which are either one-seeded and indehiscent, or else 

 take the form of schizocarps or heads of achenes, separating 

 into one-seeded segments. The seeds are thus protected both by 

 pericarp and testa, which is possibly of value in enabling them 

 to resist the rotting eft'ect of prolonged submergence^. It is 

 interesting in this connexion to compare, for instance, the fruits 

 of Plantago major and of the closely related aquatic, Littorella 

 lacustris^. The Plantain has a pyxidium capsule, with a thin 

 elastic wall, opening by means of a lid and containing a number 



1 Fauth, A. (1903). 2 Guppy, H. B. (1906). 



^ The protection of the embryo in certain aquatics is considered by 

 Marloth, R. (1883). 



A.W.P. 16 



