DISEASES OF THE ROSE. 209 



this larva. As soon as it is perceived in April, that the temperature has pjissed 

 beyond 12 to 15 degrees, and that the rose-trees put forth sprouts, they should be 

 examined with care. Persons having good eyes, or by using a magnifying glass, 

 can see the small punctures made in the arm-pits of the leaves, by the saw of the 

 fl}', and if they are sufficiently fortunate to perceive the small worm, he can be 

 taken out with a fine long needle, or simply with a pin. Sometimes it is not 

 discovered until some little time after it has commenced digging. It is not then too 

 late to extract it by the same process. I have also fitted a handle to a long needle, 

 for facilitating the extraction of the worm at the period of its birth. Its appear- 

 ance is most usually indicated by the small heap of red dust at the mouth of the 

 opening at which it entered. The point of the needle may then be thiust through 

 the hollowed peduncle, without injury, especially if the needle be very fine, and 

 the ravage far advanced. It is sufficient to crush the animal by pressing the 

 peduncle between the fingers; but carefully, lest the branch should be destroyed 

 at the same time. The slightest touch destroys this feeble worm. But if the 

 branch be already considerably injured, which may be known by its drooping, 

 there is, then, no longer, any remedy. The branch must be cut ofi", particularly 

 if the animal is yet in it, which is indicated by the absence of the hole for egress. 

 It has, in most cases, already escaped when the havoc has advanced to that 

 extent. The peduncles of rose-trees may be hardened by piercing them with a 

 needle, before the worm penetrates them. A cicatrice growing there prevents the 

 digging of this troublesome guest, and stays its destructive course. 



Notwithstanding the inefficiency of the means in our possession to accomplish 

 it, every attempt .should be used to destroy this insect in its perfect state. The 

 most simple consists in pursuing it closely with a net. A hundred an hour may 

 be caught by exercising a little perseverance in the pursuit. I imagined I might 

 keep the saw-fly from the rose-tree by covering the top with gauze. In spite of 

 all my precautions, some few, at least, would succeed in obtaining entrance ; 

 perhaps I was too late, although I usually did it before the development of the 

 sprouts, ^t other times, if I were so fortunate as to protect them from the saw- 

 fly, I desn-oyed my rose-trees by depriving them of air. For one can scarcely 

 conceive how effectually .so thin a net prevents its approach, or, at least, its circu- 

 lation, as may be seen by the change of the leaves as they unfold. Moreover, 

 other larvae, the false caterpillar particularly, retreat, in great numbers, into the 

 parts which contain them. Another difficulty is, that this experiment can be made 

 only on tree roses, which have trunks. For the others always having a great 

 quantity of branches, render their complete destruction almost impossible. I will 

 here state, however, that when I have put gauze around rose-trees which the saw- 

 fly had already attacked, they have all come out of their passage and escaped 

 without my being able to seize one, or even to discover where the)- made their exit. 



For the same purpose (protecting rose-trees from the saw-fly), I have covered 

 the j'oung sprouts with oil by means of a small brush. I had there another result. 

 There were no larvse, but I had destroyed the vegetation of my rose-trees. I . 

 ought, however, to confess that I have not persevered in this kind of experiments. 

 The liquid should be repeatedly tried and varied. For one may possibly be dis- 

 covered which will not injure the vegetation, at the same time that it will expel 

 the insects. Ver\- odorous liquids may have such a property. Pure water does 

 not seem to disturb them. I have seen rose-trees utterly destroyed in spite of an 

 almost continual rain. Perhaps they had been punctured before it commenced. 



The best and most certain preservative of rose-trees, as I have already shown, 



18* 



