/j/sci/s ill Orc/iii/ I/oiiscs. 1 1 1 



with some coiiuiiuu on'liids and liydrui yauic acid j;as. This ^'us (im l>e 

 used for such delicate j)Ian!s sis inaideidiair feru without injury and U 

 fatal to all forms of animal life, hut its elfect on onhids has not lK*en 

 ohserved. If there is much moisture on the jdants this i^m.s loses much 

 of its jjotentT, ami the air durinir fumigation should Ik; dry. Itfl effects 

 in an orchid house miijlit not therefore be as successful as uiuhr (jther 

 circuuLsiances. It is ceriaiidy worth trying, however, as fumigation witii 

 tolwcco, etc., would have little effect on theiie creatures that are caiwing 

 the annoyance. 



(ireat care should Im* exercised in the use of hydrocyanic acid gsis, as it 

 is a most dangerous poison to man. 



Should Mr. Colman think it advi.sahle to experiment with this 

 iu.secticide, information as to procedure can he sent him. 



There does not seem to he any other way in which these pests c;in be 

 eradicated under the conditions necessary for orchid cultivation. 



Fred. V. Tiieou.\ld. 



Gatton Pabk, Surbey, 



29</i July, 1902. 



To Pkofes.sou L.vxkesteu, 



British Museum (Nat. Hist.) 

 Cromwell Road, S.W. 



Dk.vr Sir, — In further reply to the interesting report of Mr. 

 TheolKild of the I'lst, I ha\e had an opportunity of a careful discu.ssiou 

 of the j)()inLs raised with my gardener. 



I understand the report to throw considerable doubt upon the 

 prohtbility of the larva- of the Sciarin;c being harmful. Under the 

 ciivumsUiUces, and as it seems certain that the Collend>ola or Spring-tails 

 are, I suggest that we ignore the former, especially as we have not l)een able 

 to oliserve them and have no actual eviilence of their cjuising mischief. 



There will be no dilRcidty in adopting the suggestion tiiat the effect 

 of hydrocyanic acid gas upon orchids shall be a.scertained by e.\iK.'riments. 

 It is iK'licvcd, liowever, that, u.sed in moderation, it will not l)e harmful to 

 them. It is certainly unfortunate that it.s effect is likely to l>e minimised 

 by moisture. The moi.stuix' on the moss, etc., can lie reduced, but it is 

 such an essential feature in the early stages of orchid growing that it 

 Would have to l>e donu with gnat cjire and not for any length of lime. 

 Should it Ik' the young Sj)rini:-tails which are most largely res|Kiiisibl(' fur 

 the nu.s<hief, material relief from these {k'SLs miglit Ihj sciurt-d by an 

 application of the gns l)efore the seed is sown or l»efore the germinating 

 plants are transferred thento and when the comjvist is in a jn-rfntly dry 

 state. A gotnl deal depends upon their habits, but I am writing on the 

 lussumption that iIk- young may not develop very (|uickly or Iw able to 

 reach the iK)t« l>ofoR' the plants are surticiently strong to tflke care of 

 theniselve.s. It seems diniculi to place th«' jx'ts in such a position a.s to Im- 

 out of rea<"h of the adult Spring-tails, l>ut we will gladly cxpcriiiHiit if any 

 suggestion can be made. We have now nlaceil some of the pots on n zinc 

 tray on stands, which seems to have niinimise«l the mischief somewhat. 

 Althouirh the more ortholoi wav of niisim: the scc«l seems to Ik; to sow it 



