1 8 ALISMACEAE [CH. 



surface of the mericarps is non-wettable and they often float 

 for long periods, sometimes until frost produces waterlogging 

 of the fruit wall. After the decay of the latter, the embryo is 

 still protected by the cuticularised testa 1 . 



The petioles of Sagittaria sagittifolia contain lacunae crossed 

 at intervals by diaphragms (D in Fig. 8). A peculiarity, which 

 has been recorded in connexion with the life-history, is that not 



st 



FIG. 7. Sagittaria sagittifolia, L. Base of plant dug up July 16, 1910, showing 

 remains of old stolon (stj from plant of previous year bearing tuber (t) with scale 

 leaves (sc) ; the plant of the current year has also produced a stolon (st z ) which will 

 give rise to a tuber later in the autumn. At this stage the old tuber is dry and 

 spongy in texture, having contributed all its reserves to the plant which has sprung 

 from it. ( nat size.) [A. A.] 



only roots but also stolons may sometimes break through the 

 diaphragms of the leaf-sheath of living leaves and penetrate as 

 far as 10 cms., running in the petiole parallel to its long axis 2 . 

 It would be interesting to know whether any significance is to 



1 Fauth, A. (1903). 2 Klinge, J. (1881). 



