DIVISION II. 



THE PHYSIOLOGICAL OPERATIONS OF PLANTS. 

 Section i. The Nutrition of Plants. 



A. Absorption (a~) of Water and Dissolved Minerals. 



It is a familiar fact that water and minerals are absorbed 

 by the higher plants through their roots. It is needful there- 

 fore to begin a study of absorption by an investigation into the 

 structure of the absorbing parts of roots. 



18. What is the structure of the absorbing part of the root of 

 a typical land plant ? 



I.e., what is the structure of the tip, of the hairs, of the 

 tracheae ? \Yhat is the distribution of the ducts, and the rela- 

 tion of the hairs with them ? What is the relation of the root- 

 hairs to the soil-particles ? 



Answer from a study of the roots of mustard and oats, 

 grown both in germinators and in soil. Construct a diagram 

 of the structure of the young root as an absorbing apparatus. 



Root-tips and hairs in perfect condition may be obtained thus: in a 

 small, very porous flower-pot saucer (or in a Zurich germinator) place 

 seeds of mustard, soaked an hour or two, and of oats, soaked overnight ; 

 cover with a similar saucer, and set in a dish of water deep enough to- 

 keep the inside of the seed saucer always moist, though not wet. (See 

 page 44.) Three days will bring them to perfection.* 



* An extremely easy and very effective method of obtaining perfect root-hairs for 

 general student work is the following : Take a flower-pot, any size (say five-inch) ; 

 cork the hole in the bottom ; throw into it with some force a small handful of mus- 

 tard-seeds soaked a few hours ; the seeds with their mucilage will stick to the pot ; 

 invert the pot and set in a saucer of water for two or three days. 



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