xvii] TURIONS 219 



stored with food material, and protected externally in some way, 

 become detached from the parent and pass the winter either 

 floating, or resting at the bottom of the water. In the spring 

 they expand, produce adventitious roots, and rapidly develop 

 into full-fledged individuals. Certain plants, also, which do not 

 actually produce independent turions of a specialised type, 

 show transitions towards such a development. If shoots of the 

 Greater Spearwort, Ranunculus Lingua^, are left in water over 

 the winter, they rise to the surface in the spring in a partly 

 decomposed state, but bearing healthy buds in the axils of their 

 leaves ; these become detached to give rise to new plants. Elodea 

 canadensis (Fig. 34, p. $S) '^'^^ Stratiotes abides (Fig. 32, p. ^'^^ 

 again, produce primitive reproductive buds, which do not imme- 

 diately become free, but germinate while attached to the parent 

 plant 2. The apices of the shoots of Ceratophyllum are clothed 

 in autumn with leaves which are more crowded and of a deeper 

 green than those of the rest of the shoot, but, as we have already 

 pointed out^, they can scarcely be said to form definite winter- 

 buds. 



Certain turions showing a high degree of specialisation have 

 already been mentioned, e.g. those of Hydrocharis (pp. 47-49), 

 Potamogeton (pp. 66-69), the Lemnaceae (pp. ^ S-ll\ Aldro- 

 vandia (p. no), and Utricularia (pp. 101-IC3). The difference 

 between the normal foliage leaf and the protective outer leaf of the 

 turion, in the case of U. intermedia^ is shown in Fig. 143, p. 220. 

 Among the British plants to whose wintering habits we have not 

 yet TeitYvtd,Myriophyllum verticillatum^ affords a striking example 

 of turion formation. In August the plant may be found simul- 

 taneously producing flowers and winter-buds (Fig. 144, p. 22 1). 

 Early in October the ragged shoots may be seen floating, with 

 here and there a compact turion (r), distinguished against the 

 faded brownness of the parent plant by its vivid, dark-green hue. 

 These winter-buds become detached during the cold season, and 



1 Belhomme, (1862). 2 Qiuck, H. (1906). See p. 87. 



* The winter-buds of Myriophyllum were noted by Vaucher, J. P. 

 (1841). 



