xv] WATER FORMS OF LAND PLANTS 199 



A and E) and Menyanthes trijoliata^ but also by typically terres- 

 trial plants such as Achillea ptarmica^ Trifolium resupinatum 

 (Fig. 131 5) and Cuscuta alba (Fig. 131 A). "Gliick^ has also 

 produced experimentally a submerged form oi Iris Pseudacorus. 

 Seeds of terrestrial plants may sometimes germinate and reach 

 a considerable development while entirely submerged. The 



Fig. 129. 



Fig. 130. 



Fig. 131. 



Fig. 129. Caltha pahistris, L. The two leaves with long petioles belong to the sub- 

 merged form: the middle leaf is a corresponding air leaf of the land plant. (Re- 

 duced.) [After Gliick, H. (191 1), Wasser- und Sunipfgewachse, Bd. iii, Fig. 3, p. 65.] 



Fig. 130. Cirsium anglicum, D.C. (=Cnicus prafensis, Willd.). A, land form, 

 B, water form. [After Gliick, H. (191 1), Wasser- und Sumpfgewachse, Bd. iii, 



Figs. I a and b, p. 16.] 



Fig. 131. Cuscuta alba, J. and C. Presl, forma submersa. A, parasitic on water 

 form of Echinodorus ranunculoides, (L.) Engelm. B, parasitic on the form of Tri- 

 folium resupinatum, L. with floating leaves. (Reduced.) [After Gliick, H. (1911), 

 Wasserund Sumpfgewachse, Bd. iii, p. 114, Figs. jA and B."] 



present writer has noticed Horse Chestnuts sprouting freely 

 in the mud at the bottom of a stream : one which was measured 

 had a plumular axis more than i inch in length, and a primary 

 root of 3^^ inches. 



In connexion with Gliick's record of a submerged form of 



1 Gluck, H. (191 1). 



