SCIENCE-GOSSIP. 



197 



itself up, and on examining it when ten days old I 

 found the cotyledons had coiled up, as in fig. /, 

 without any change in the radicle or any appearance 

 of roots ; nor had the cotyledons increased in size 

 as is the rule with the seedlings free in the water. 

 ■When it was a month old, it showed no alteration ; 

 but the coiled-up cotyledons under the mud were 

 beginning to decay. 



heated, the plants matured their fruit in quantity 

 in August in the shallows of a pond in the Home 

 Park, Hampton Court. The depth here was only 

 a few inches, and for a fortnight in mid-August 

 the temperature of the water always rose above 

 eighty degrees Fahr. in the afternoon, often reach- 

 ing ninety, and occasionally ninety-five, degrees. 

 During this spell of tropical weather, when the air 



Ceratophvllum demersu . 



A. Germinating fruit. 



B. Embryo just freed by germination. 



C. Germinating embryo two or three days old. 



D. Ditto, a week old. 



E. Ditto, kept in deep shade. 



F. Lower part of a seedling, ten days old, which had been developed under the mud. 



Although this plant often flowers in the heated 

 shallow waters of ponds and in the parts of sluggish 

 rivers that are out of the current, in this climate, 

 as before remarked, it rarely matures its fruit. In 

 various localities I have never found the fruit 

 beyond its early stage, and out of a number of 

 plants that flowered in my greenhouse all produced 

 young pale-coloured fruits which, when about half- 

 size, fell off and rotted at the bottom. However, 

 during the drought of the hot summer of 1S93, when 

 many ponds became very low and were excessively 



in the shade on some days was ninety degrees, the 

 Thames did not rise above seventy-five degrees, 

 whilst its tributary, the Mole, was two or three 

 degrees cooler (seventy-two to seventy-three 

 degrees). Under such exceptional conditions of 

 temperature in the Home Park pond, this plant 

 matured its fruit ; but in places in the River Mole, 

 where it grew luxuriantly, I found no fruit. For 

 these and other reasons I found an explanation of 

 the plant flowering so frequently in this country 

 without bringing its fruit to maturity, in a higher 



