182 PLANT PHYSIOLOGY 



4. In ferns, the sperms are attracted to the female gamete by 

 malic acid produced by the archegonium. 



5. They may serve as a sort of reserve food or temporary stor- 

 age product. The calcium oxalate crystals in Sterculia platani- 

 folia dissolve at blooming time, and starch appears in the cells 

 which contained the crystals, which here seem to be reserve foods 

 rather than excretory products. 



That the acids are associated with carbohydrates, from which 

 they probably arise is shown by the fact that the amount of acid 

 present depends in a general fashion upon the amount of carbo- 

 hydrate; and plants grown under "long day" conditions, i. e., 

 which produce more carbohydrates, contain more acids than plants 

 illuminated for only a short period daily. In Phaseolus and Semper- 

 vivum, however, at 35° and in light, not so much acid was found 

 as in the dark or at 5°, i. e., in conditions favorable for producing 

 carbohydrate, less acid was found. 



Nitrogen Bases. — The vegetable bases all contain nitrogen 

 and may be considered as derivatives of ammonia, which can form 

 salts by combining with acids and thus shows its basic nature. 

 The fact that nitrogen may be pentavalent and combine with 

 five different kinds of radicals increases the number of basic com- 

 pounds which in this way can be derived by substituting other 

 radicals in the ammonia for the hydrogen atoms. 



/N M 



N-H //& 



X C1 



ammonia ammonium chloride 



On the basis of their structure the plant bases may be divided into 

 three groups,— the natural bases, the alkaloids, and the purine bases. 



Natural Bases.— The natural bases or amines are open-chain 

 compounds with substituted radicals in the ammonia as described 

 above. Among these are choline and muscarine, which occurs in 

 the poisonous mushroom, Amanita; but they are also found in 

 fruits, seeds, roots, etc. Choline has the formula 



N(CH 3 ) 3 OH 



I 

 CH2CH2OH 



