102 



HOUSE, GARDEN, AND FIELD 



strongly adaptive in its origin, but it appears to be so 

 ancient in both cases as to have become ancestral, that is, 



perpetuated rather by long-con- 

 tinued inheritance than by the 

 exigencies of present conditions. 

 In spite of their aquatic situa- 

 tion the water-lilies are much 

 beset with caterpillars, the larvae 

 of a moth known as the Brown 

 China Marks. The larva is found 

 in early summer on pondweed, 

 and afterwards devours the leaves 

 of water-lilies and some other 

 aquatic plants. It makes a 

 flattish sheath out of two pieces 

 of leaf, and thus completely 

 conceals its own body. The 

 sheath, even if submerged, is 

 kept full of air, for the larva 

 has no gills, and breathes solely 

 by spiracles. The pupal stage 

 is passed within the same sheath, 

 but is never submerged. Other 

 insects attack the water-lilies in 

 ways of their own. A Dipterous 

 larva mines the leaves, and ex- 

 cavates long winding galleries in 

 their thickness. The roots tocks 

 harbour a beetle-larva (Donacia), 

 which, though it lives at the 

 bottom of a pond or river, is 

 an air-breather. It procures the 

 air which it requires by tapping 

 the air-filled cavities of the root- 

 stock, and filling its respiratory 

 tubes through spiracles constructed for this very purpose. 

 It interested me greatly, when visiting the lakes of the 



FIG. 30. Seedling of yellow 

 water-lily, magnified. To the 

 left are seen the seed, still enclos- 

 ing the seed-leaves, the radicle, 

 and a small lid, which opens to 

 allow the escape of the radicle ; 

 in the centre of this lid is the 

 micropyle. To the right is a 

 bud, from which are given off 

 two leaves, one long and strap- 

 shaped, the other folded, besides 

 an adventitious root. 



