212 PHYSIOLOGICAL BOTANY. PART II. 



altered by the action of alcohol, ether, or cold water ; 

 but in hot water the pellicle bursts, the contained 

 matter exudes, and the whole mass becomes a paste. 

 The specific gravity of fecula is about 1'53. It 

 may be obtained from the pulp of fruits, tubers, succu- 

 lent stems, and other parts of various plants. That 

 which is derived from corn and the potato is fami- 

 liarly termed starch. Sago (from the stems of a palm), 

 tapioca (from the tubers of the Jatropha manihot), 

 arrow-root (from the rhizomata of the Maranta arun- 

 dinacea), are all so many varieties of fecula. This 

 substance is highly alimentary and is largely stored 

 up in various parts of vegetables where it forms 

 magazines of nutriment, apparently destined for the 

 future development of the buds and ripening of the 

 seed. It is a material of all others the most im- 

 portant as an article of human food, and is providen- 

 tially provided for our use in the greatest abundance. 

 It bears a striking analogy to the fat of animals, even 

 in the general structure of its component parts accord- 

 ing to some, but more evidently in the uses to which 

 it is subservient in the economy of vegetation. The 

 formation and subsequent re-absorption of fecula is 

 rendered very evident, by comparing the different quan- 

 tities found in plants of the same species at different 

 seasons of the year. The following table shows us 

 f he gradual accumulation which takes place in 100 

 , pounds of potatoes between August and November, and 

 the subsequent diminution from March to May : 



Aug. Se])t. Oct. Xov. March. April. May. 



10 14 14| 17 17 13$ 10 



(198.) Plants containing Fecula. The following 

 list contains a few of the principal plants which furnish 

 fecula in the greatest abundance, and the figures givi- 

 the percentage yielded by the several organs from 

 which it is extracted. These numbers may also be 

 considered to a certain extent indicative of the degrees 

 of nourishment which each is capable of affording : 



