40 LIMNANTHEMUM [CH. 



produced and the axis ends in a cymose inflorescence with a ter- 

 minal flower. The shoot morphology is somewhat puzzling, and 

 remained obscure until it was elucidated by Goebel 1 who 

 studied L. indicum and other species from this point of view. In 

 plants of Limnanthemum, examined at the flowering season, it is 

 found that a long stalk given off from the rhizome appears to bear 

 both a lamina and flowers, or, in other words, that the flowers 

 seem to arise laterally from a leaf-stalk. In reality this long 

 stalk is however the axis of the inflorescence, and only the short 

 segment of leaf-stalk above the inflorescence is actually the 

 petiole. This petiole has a short, sheathing base, which in 

 youth surrounds the inflorescence. In development, the foliage 

 leaf pushes the growing point to one side and comes to occupy 

 the terminal position. Goebel considers that this peculiar mode 

 of growth confers a definite biological advantage. The breadth 

 of the leaf-surface resting on the water gives the inflorescence 

 the necessary support, while the elongated inflorescence axis 

 forms a substitute for both the elongated petiole and peduncle 

 of the Waterlilies. The flower is raised well above the surface 

 of the associated leaf and thus rendered conspicuous to insects. 

 The products of assimilation find their way by the shortest 

 route to the ripening fruit, whereas in Castalia and Nymphaea 

 they have to descend many feet to the bottom of the water and 

 then rise again a similar distance to the flower, because there 

 is no connexion between lamina and flower, except via the 

 rhizome. But, as Goebel suggests, such an arrangement as that 

 met with in Limnanthemum would have less value in the case of 

 the Waterlilies, because the Nymphaeaceae store so much food 

 in their rhizomes that the ripening fruit is not dependent 

 upon the products of contemporaneous assimilation. It would 

 be utterly unsafe, however, to suppose that the morphological 

 differences between the Waterlilies and Limnanthemum are to be 

 explained on such simple adaptational lines, though it is obvious, 

 from the success which both families achieve, that their re- 

 spective types of construction must be well suited to aquatic life. 

 1 Goebel, K. (1891) and (1891-1893). 



