TRANSACTIONS 



BOTANICAL SOCIETY OF EDINBURGH. 



SESSION LXXXVII 



The Seedling Structure of Salix pentandra, Linn. 

 By Ian W. Seaton, B.Sc. (With PI. VIII.) 



(Read 16th November 1922.) 



So far as I can ascertain, no record has been made, hitherto, 

 ■of the germination of the seed of Salix pentandra. The seeds 

 are minute and are adapted for wind dispersal by the possession 

 of a parachute of long silky hairs. This parachute is an arillar 

 structure and the hairs arise in groups of three or four from a 

 ring formed of their contiguous bases. This ring fits on to the 

 lower or radicle end of the seed (fig. 1). On moistening, it 

 expands slightly and is then completely and easily detachable. 

 The seed is pear-shaped and has a thin brown testa which 

 conforms in shape to the enclosed embryo (fig. 2). 



The embryo has oblong-oval, plano-convex cotyledons, the 

 plane, adaxial faces of which are closely adpressed, a short, 

 stout hypocotyl which ends abruptly, and a very small, terminal, 

 peg-like radicle (fig. 3). The whole embryo, with the excep- 

 tion of the radicle, is green and shining. 



The seed is exalbuminous, the food reserve being stored in 

 the cotyledons, which are comparatively large and fleshy. 

 The embryo is nearly straight in this resting' condition. The 

 first process of germination is the elongation of the hypocotyl. 

 Growth is more rapid along one side, and the seedling becomes 

 bent in consequence. This arching, convex towards the soil 

 surface, splits the seed coat and the curved middle part of the 



TRANS. BOT. SOC. EDIN. VOL. XXVIH. 14 



