1€4 ORDER HOMOPTERA. 



want of proper nutriment, or by other neglect. It is true that a vigorous plant or animal 

 may become infested with parasites ; but these cases are exceptions, and not the rule. We 

 have therefore every motive to induce us to protect and nourish our plants and animals, 

 both for the greater profit they will render us, and as a security against disease and the 

 attacks of parasitic animals. 



Atmospheric Blighti 



There is a disease among cultivated herbaceous plants, the origin of which is not deter- 

 mined. The plant, as the June pea, for example, begins to dry and whiten below : this 

 dryness extends upwards, and sometimes so rapidly that the crop of pease is lost ; but 

 whether this be the case or not, the crop will be greatly diminished, and the early death 

 of the whole plant is the consequence. The disease may be said to be a premature decay 

 and death of the plant : it is equivalent to a blight, or to the potato disease. The question 

 that arises respecting it, is. Is it due to an insect, or to atmospheric causes 1 The answer 

 to this question is neither definitely negative nor positive. No insects have yet been de- 

 tected upon the pea ; and yet its root, which has not perhaps been sufficiently examined, 

 may disclose some insect that brings on this decay. As to the atmosphere, physiologists 

 may well differ : we ascribe to changes of the weather, those diseases and injuries that 

 cannot be referred to the attacks of insects. Remedies have not been proposed ; but it is 

 suggested that a change of seed may divert the calamity, or perhaps soaking the seeds in 

 muriate of ammonia or a weak solution of copperas, and then rolling them in plaster. 



The lychnidea becomes sometimes affected with a white mouldiness, which makes its 

 appearance upon the leaves early in July, and destroys the beauty of the plant, beginning 

 upon the lowermost part of the leaf, and extending upwards until the whole is coated with 

 a fibrous matted mucor. It does not appear to be of animal origin : under a single lens, I 

 have not been able to discover any thing that looks like the work of an insect. The ques- 

 tion is. Whether this fungus is the consequence of a too feeble vital action ; or, to speak 

 more cautiously, whether what we call vital actions are enfeebled by any causes other than 

 those which may be attributed to wounds by insects ? The parenchyma of the leaf is not 

 destroyed, but the surface is covered with a white fibrous fungus, analogous to the coverng 

 of the gooseberry when affected with mildew. 



In undertaking to assign a cause for effects of the foregoing kind, it should not be for- 

 gotten that a minute puncture may result in the production of a 'fungous growth : the 

 juice exuding from a wound, whether poisoned or not, undergoes a change that fits it for 

 the growth of fungi, which may be in some instances small and invisible, while in others 

 they extend over large surfaces, and, as in.the lychnidea and gooseberry, occupy in time 

 the whole leaf, or the whole surface of the fruit ; so that a puncture, to us invisible, and 

 which may be made by an insect, can yet be detected in its consequences. The greater 



