No. XV.B.] APPENDIX. 233 



diseased tubers are deficient in starch, and starch-makers cannot obtain 

 from them more than half the usual quantity. 



Examining this question physiologically, then, we find on the plant a 

 certain insect, and that on a part of the plant, viz. the leaf, which is 

 destined to elaborate solid matter for the growth of the whole. Anatomy 

 and physiology also show that the insect, by its conformation, is calculated 

 to take away and feed upon the sap or vital fluid of the plant, which was 

 destined to form solid and healthy vegetable matter. The microscope 

 demonstrates that a due and healthy proportion of solid material does not 

 exist in the diseased tissue ; and chemical analysis also fully confirms the 

 fact. So that the cause, the progress, and the ultimate effects of this 

 vegetable malady are clearly and satisfactorily explained by the conjoint 

 evidence of observation, physiology, anatomy, and chemistry. This aphis 

 produces the same results in all plants, its operations on which I have 

 watched one after the other, and I am now watching others go through 

 the same progress. Some strong plants are not easily affected by the 

 attacks of the aphis ; for example, a large beet-root vigorously resists the 

 ravages of these creatures, and requires, at least, ten thousand of them 

 to destroy it. As there have been many different plants attacked and 

 destroyed by aphides, these creatures have accordingly received different 

 names, usually with reference to the plant on which they subsist ; and I 

 am told there is a book in the British Museum in which all these are 

 recapitulated. It appeared to me, however, that the aphis giving rise to 

 the potato disease also commits great or equal ravages on many other plants 

 good for the food of man, or otherwise useful to him ; but, not being able 

 to find that any characteristic name was applied to it, I carefully consulted 

 with Mr. Thompson, the intelligent librarian of this institution, and, after 

 unsuccessfully ransacking the library for some applicable cognomen to 

 give this individual, we agreed to give it a name characteristic of its 

 depredations, and called it the vastator, or destroyer. 



When a scarcity of food exists, or future plenty is doubtful ; or when 

 famine seems impending ; and when, at the same time, we have authentic 

 accounts of numbers of our destitute fellow-creatures starving through lack 

 of food, it becomes an imperative duty to exercise our utmost ingenuity to 

 adopt any substitutes for the natural food of man that can be proved avail- 

 able, and several such have been suggested. Mr. Hamp, an intelligent 

 gardener, has proposed a root, called the Apios tuberosa, to be used as a 

 substitute for potatoes, and I have no doubt it would answer the intention 

 remarkably well. I have tried experiments in the manufacture of various 

 kinds of bread, such as carrot bread, turnip, mangold- wurzel, rice, and 

 parsnip bread, &c. The vegetable is boiled up with an equal quantity of 

 flour, and is afterwards baked in the usual way. Some of these kinds of 

 bread are most delicious, several of which are on the table before me. But 

 by using such articles we secured no gain to the available stock of human 

 food, and I, therefore, tried what hay would do if manufactured into 

 bread. You all know its nutritive properties to various animals, and I 

 have no doubt that, both from the result and from analogy, it contains 

 much nutritive matter that would be serviceable and acceptable to man in 

 a time of famine. Hay made into biscuits is preferable to hay bread. The 

 hay is ground into an impalpable powder, and, when mixed with an equal 

 quantity of flour, is to be made up and baked in the usual way. Iceland 



