xv] WATER FORMS OF LAND PLANTS 199 



A and 5) and Menyanthes trifoliata^ but also by typically terres- 

 trial plants such as Achillea ptarmica, Trifolium resupinatum 

 (Fig. 131 5) and Cuscuta alba (Fig. 131 A), Gluck 1 has also 

 produced experimentally a submerged form of 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 palustris, 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 Gluck, H. (1911), Wasser- und Sumpfgewachse, Bd. in, Fig. 3, p. 65.] 

 FIG. 130. Cirsium anglicum, D.C. (=Cnicus pratensis, Willd.). A, land form, 

 B, water form. [After Gluck, H. (1911), Wasser- und Sumpfgewachse, Bd. in, 



Figs, i a and 6, 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 Gluck, H. (1911), 

 Wasserund Sumpfgewachse, Bd. in, p. 114, Figs. 7 A 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. (1911). 



