227 



4. THE CORM. 



It is for its starchy conn or "root" that the kalo is chiefly raised, 

 ahhough other portions of the plant have some value as food. A 

 full-i^Tovvn conn of average size is as large and as heavy as a 

 large sweet potato. It is covered with a fihrous or scaly bark, 

 especially towards the siininiit. just beneath this outer bark is 

 an inner layer, which may he white, rose, greenish, or purplish 

 in color, depending u])()n the variety. T\ie interior of the raw 

 corm is usually light gray with a slight-bluish tinge, hut in some 

 varieties may be yellow, orange, rose, or even purple. 



r^or many years the acrid or toxic effect of certain aroids was 

 not understood. Professors Pedler and Warden, of thj Depart- 

 ment of Chemistry, Calcutta University, first demonstrated the 

 presence and action of the calcium oxalate crystals. The fol- 

 lowing" excerpts from their paper in the Journal of the Asiatic So- 

 ciety of Bengal, \'o\. ?7, Part II, No. 1, for 1888, prove of interest 

 in this connection. Their experiments were performed upon Co- 

 locasia -z'irosa Kunth, which at that time was called ;m .Iniui. 

 After prolonged and varied chemical tests they stated that "The 

 examination of the ash thus failed to afford us any clue to the 

 physiological action of the fresh tubers. 



"It now occurred to us that possibly the painful eft'ecl jM-oduced 

 by Arum when in contact with the tongue, etc., might l)e due to 

 mechanical causes. A microscopic examination of a section of a 

 tuber revealed the presence of very numerous bundles of needle- 

 shaped crystals, and we also found similar crystals in the leaves 

 and stems. These crystals were seen under the microscope to be 

 insoluble in cold acetic acid but easily soluble in cold diluted nitric 

 or hydrochloric acid. '■' * ''^ There appears to us to be no 

 reason to doubt the fact, that the whole of the physiological symp- 

 toms caused by Arums are due to these needle-shaped crystals of 

 oxalate of lime, and that the symptoms are thus due to purely 

 mechanical causes. Bearing in mind the action of re-agents on 

 calcic oxalate, the reason why mere boiling in water failed to 

 deprive them of their activity is explained by the insolubility of 

 oxalate of lime in water. Again, the action of dilute acetic acid, 

 even at temperatures of 100 degrees C, in slightly lessening the 

 activitv of the tubers, is due to the very slight solubility of oxa- 

 late of lime in that acid. And, lastly, the complete loss of all 

 physiological action when the tubers were treated with dilute 

 nitric or hydrochloric acid is evidently due to the ready solubility 

 of cafcic oxalate in those mineral acids. And these assump- 

 tions, as we have alreadv indicated, were fully demonstrated by 

 the microscopic examination of sections of the tubers treated with 

 the re-agents we have mentioned. One point, however, remains 

 to be explained : we observed that, on drying, the tubers lost 

 practically the whole of their physiological activity. Clearly there 



