78 FAMILIAR LESSORS IN BOTANY. 



At 2 P.M. Scilla pomeridiana. 



Between 5 and 6 p. m. Silene noctiflora. 



Between G and 7 p.m. Marvel of Peru. 



Betw^een 7 and 8 p.m. Cereus grandiflorus, night-bloom- 

 ing cereus. 



At 10 P.M. Purple convolvulus. 



You will be interested in noting the fact that the same 

 flower expands at different hours here and in Paris. Owing 

 to the excess of light and heat enjoyed on the Western 

 Continent, they expand an hour or two earlier than the 

 time noted by De Candolle. But to resume the subject of 

 vegetable phenomena : 



200. The color of plants is supjoosed to be owing to a 

 substance called cliroimile, and that the variety of hues is 

 formed by the action of alkalies and acids on this chromule. 

 This substance is pure carbon, and is deposited in minute 

 grains in the vesicles of cellular tissue. Light being ne- 

 cessary for the deposition of this substance, plants growing 

 in dark places are nearly colorless. 



201. Plants have been found in deep mines, however, 

 that were green, though they had never seen the light. A 

 great many theories have been advanced to account for the 

 variety of hues in leaf, stem, and flower. 



202. "Macquart supposed it was owing to the various 

 modifications of chlorophyle being converted into two dis- 

 tinct substances on the addition or abstraction of Avater." 

 — Darhy. 



203. The coloring matter obtained from various plants 

 is of the greatest value in arts and manufactures. Madder, 

 saffron, oak, logwood, woad, indigo, give us the red, yellow, 

 brown, black, and blue dyes of commerce. These in all 



200. To what is the color of plants ascribed ? What is this chromule? Where 

 deposited ? What of plants growing in dark places ? 



201. What of some plant? fonnd in mines"? 



202. What did Macquart suppose? 



203. Of what value is the coloring matter found in plants ? Examples ? What 

 do they require ? What is a mordant 2 



