92 ORGANS AND FUNCTIONS OF PLANTS. 



Digestion. 



Plants h aving no common gullet, have moreover 

 no common stomach for the digestion of food, and all 

 the researches hitherto made respecting the conversion 

 of carbonised water (if I may thus term the sap) into 

 the fluids peculiar in smell, taste, and colour found 

 in the plant, have only led to plausible conjecture. 

 Some observations render it not improbable that, on 

 the first imbibition of the carbonised water by the 

 spongelets, it may be in part mixed with some other 

 fluid from the interior of the plant, in a similar manner 

 to the food of animals being usually mixed with saliva 

 in the mouth ; and though this may not be sufficient 

 to convert the sap into fluids of different character, it 

 may, like the animal saliva or the digestive fluid in 

 the stomach, greatly assist such conversion. 



ORGANS OF CIRCULATION. 



WHAT is popularly termed the heart (properly the 

 pith) of plants, has no resemblance whatever to the 

 organ termed the heart in animals, which is the central 

 reservoir for receiving the blood, and again propelling 

 it to all parts of the body. In plants there is no organ 

 in the least resembling such a heart ; yet the fluids, 

 notwithstanding, circulate both upwards and down- 

 wards, often with great rapidity and with considerable 

 force. On this subject various opinions are, and have 

 been, held. 



It has been the most extensively received notion, 



