Ii6 Human Physiology. 



find in the atmosphere the subtle element of its own life. When 

 fruit trees are in blossom, it is said that fruits of the same kind, 

 kept through the winter, lose their flavours, and even the stains 

 of fruits can be bleached out then as they can at no other 

 period. If aromas do not exist, then they are manufactured in 

 plants ; and what a wonderful action of vital chemistry is it to 

 make from the same elements all the odours, savours, honey, 

 acids, gums, oils, turpentine, caoutchouc, camphor, opiates, 

 poisons, all the sharp, pungent, bitter, nauseous, delicious 

 substances produced by the vegetable kingdom ! 



It is in the reproductive even more than the nutritive processes 

 in vegetables we are to look for wonderful contrivances, because 

 it is in them that life exerts its greatest force The thistle on 

 the chalk downs cannot grow stalk or leaves ; there is not soil 

 enough for that; but it makes a perfect blossom, and abundant 

 seeds, level with the fine herbage. Many plants depend upon 

 insects to bring the two sexual elements together and make 

 fertile germs. A drop of honey is formed by the flower and 

 placed in a deep receptacle ; bees or other insects scenting this, 

 enter, brush off the pollen and carry it to the stigma of the 

 same or another flower. Sometimes the insect sets free a spring 

 by which the pollen is scattered. 



The vallisneria is a water plant, male and female flowers 

 growing on different stalks. The female flowers, those bearing 

 pistils, grow on long stalks, spirally folded up at first, uncurling 

 when the flower matures, so as to bloom at the surface. But 

 the stamen flowers have short stalks. The buds form little 

 bladders which detach themselves, rise to the surface, gather 

 round the female flowers, expand, emit their pollen, perform 

 their function, and die. 



The arrangements for the distribution of the seeds of plants 

 are very ingenious. Some seeds are provided with wings, or 

 light down, by which they are wafted long distances by winds; 

 some have hooks with which they fasten to animals ; many are 



