154 INDEX. 



Hop crop often nearly destroyed by an Aphis, 91 . 



Horseradish attacked by the Aphis vastator, 85. 



Humboldt denies the existence of wild potatoes in Peru and the 

 Andes, 9, 10. 



Hyoscyamus attacked by the Aphis vastator, 84. 



Hypogymna dispar, effects of, on oaks, 98. 



Ichneumons destroy Aphides, 105. 



Indian corn attacked by the Aphis vastator, 86 ; a substitute for the 

 potatoe, 132. 



Information desired, 145 ; form for collecting, ib. 



Insects found on the potatoe plant, 61 ; plagues of the Old Testa- 

 ment, 96 ; excessive appearances of, 97-100 ; no new fact, 142 ; 

 kept within bounds by natural causes, 101, 142; generally disap- 

 pear after being in excess, 115. 



Iron contained in the potatoe, 22. 



Jerusalem artichoke attacked by the Aphis vastator, 88. 



Kirby and Spence, account of plagues of insects, 97-99. 



Lady-bird destroys the Aphides, 103 ; vast numbers of, in 1807, 104. 



Larch attacked by an Aphis, 93. 



Latham's account of the potatoe disease, 46. 



Light necessary for the growth of plants, 49 ; influence of on the 

 potatoe, ib. 



Locust, effects of, 99 ; appearance of, this year, 101. 



Mallow attacked by the Aphis vastator, 88. 



Mangel wurzel attacked by the Aphis vastator. 79. 



Manures, their influence on the potatoe disease, 54, 55. 



Marigold attacked by Aphis vastator, 90. 



Marshall's experiments on the exhalation of water by the potatoe 

 plant, 5. 



Martius, the first writer on the potatoe disease, xxvii. 



Michael le's analysis of the potatoe, 18. 



Microscope needful for the investigation of the disease, xxxii. ; de- 

 scription of a suitable one, xxxiii. 



Moisture, effect of, on the potatoe disease, 50 ; on potatoe tubers, 51. 



Mortality caused by decaying insects, 99. 



Nectarine attacked by the Aphis vastator, 90. 



Nettle attacked by the Aphis vastator, 88. 



Nitrogen exists in the potatoe, 4 ; its probable source, ib. ; its rela- 

 tive quantity in the potatoe and in other articles of food, 20, 21. 



Oat exempt from the attack of the Aphis vastator, 87 ; attacked by 

 another Aphis, ib. 



Old age of the varieties of potatoes not the cause of the disease, 46. 



Parasites of Aphides, 102. 



Parasitic life, curious instance of, 105. 



Parsnip attacked by the Aphis vastator, 89 ; by another Aphis, ib. 



Pea attacked by an Aphis, 92 ; occasional effect of the Aphis on the 

 crop, ib. 



Peach attacked by the Aphis vastator, 90. 



