138 THE NATIONAL GEOGRAPHIC MAGAZINE 



a cluster of blueberry blossoms 

 (natural size) 



towns often bring ten, or twenty, or even 

 thirty thousand dollars, and in Northern 

 cities, as for example Boston, New York, 

 Detroit, and Chicago, the annual con- 

 sumption is enormous. 



Many attempts have been made to cul- 

 tivate the blueberry for its fruit; but, 

 when given the care, protection, and 

 nourishment that man has found neces- 

 sary for the ordinary plants of agricul- 

 ture, the blueberry sickens and dies. The 

 belief ic prevalent among farmers that 

 it is impossible to transplant the wild 

 blueberry successfully. And it really is 

 impossible if, as usually happens, the 

 planting is done in the soil of a fertile 

 garden. 



What the blueberry demands is acidity. 

 In a soil so acid that ordinary plants die 

 of poison and starvation, the blueberry 

 thrives, luxuriating in flower and foliage 

 and fruit. That a plant should grow 



better in an acid soil than in a fertile one 

 is contrary to what has been regarded as 

 one of the fundamental principles of 

 agriculture. 



Ordinary agricultural plants absorb 

 their nitrogen from the soil in the form 

 of nitrates. From the cumulative re- 

 searches of a group of scientists who 

 have exhaustively studied the question 

 for a generation, it has been established 

 that the production of nitrates in the 

 soil is brought about by certain micro- 

 organisms known as nitrifying bacteria; 

 and, furthermore, that the ability of 

 these bacteria to manufacture nitrates is 

 destroyed by acidity. Growing as it does 

 in an acid soil, the blueberry is therefore 

 squarely up against the question how it 

 shall get its nitrogen. To the individuals 

 of the plant world the nitrogen problem 

 brings about the same tragic situations as 

 does the bread problem to the human race. 



PLANTS THAT TRAP INSECTS LOR POOD 



. One group of acid-soil denizens, the 

 insectivorous plants, has solved the ni- 

 trogen question in a singularly direct 

 way. They entrap insects and digest 

 and absorb their nutritive parts. Of 

 such habits among our native plants are 

 the sundews (Drosera) , the pitcher 

 plants (Sarracenia) , the bladderworts 

 (Utricularia) , the butterworts (Pingui- 

 cula) , and the Venus' flytrap (Dionaea) . 



Another method of getting nitrogen 

 in acid soils is represented by the Euro- 

 pean lupin. These plants have on their 

 roots living tubercles within which grow 

 certain bacteria. It has been found to 

 be the function of these bacteria to take 

 the nitrogen of the atmosphere and con- 

 vert it into some, chemical combination 

 in which the lupin plant can use it. The 

 very similar tubercle bacteria of the 

 roots of clover and other cultivated legu- 

 minous plants have been much studied in 

 the last 30 years, and the fact of the 

 fixation of atmospheric nitrogen by them 

 has been fully established and is every- 

 where recognized in agricultural prac- 

 tice. The blueberry gets its nitrogen by 



