THE WEEDS OF NEW SOUTH WALES. 57 



Meaning of Name. The derivation of the word Spurge is via the French, 

 from the same word as " purge/' indicating its medicinal effects. The word 

 is applied to all species of the genus Euphorbia, and I would add that it ia 

 far too drastic and uncertain in its effects to be safely used as a purgative 

 medicine. 



The word " petty " is from the French petit, small, and indicates that it 

 is a small plant in comparison with some others. 



Economic Value. In common with the rest of the Euphorbias, it has from 

 time immemorial been used in Britain and Northern Europe as a wart-cure, 

 and hence the name " Wart-weed," applied to it and some other allied plants. 

 In country districts when local irritation is caused by its application, a very 

 old remedy is to apply oil freely. 



For some years past the juice of this little plant has beeen recommended 

 (to my knowledge) by Sydney physicians of the highest standing for the 

 treatment of rodent ulcer, and I have seen cures effected by its means. But 

 I certainly would not recommend its use (except for warts) unless under the 

 care of a physician, for the juices of such plants are too dangerous to be 

 employed except under proper safeguards. 



From the note which follows, it will be observed that the milky juice 

 (latex) affects the photographic plate, and it may be that it contains some 

 radio-active principle which explains the cure to which I have alluded : 



ACTION of the latex of Euphorbia peplus on the photographic plate.* 



The milky juice or latex of this plant has been employed by surgeons for the 

 treatment of rodent ulcer. It has occurred to us to test whether the dried latex 

 has any action on a photographic plate. A thin layer of the juice is spread on, 

 glass and is dried. A photographic plate is placed a little distance above the 

 dried film. When the plate is developed after three to seven days an image of 

 the film appears on the plate. If a word be written with the juice a well- 

 defined photograph of the word appears on the plate. Such an image appears 

 when the distance between the film and the plate is not more than one centi- 

 metre. The thicker the film of dried juice the more dense is the image on the 

 photographic plate. If tissue paper, thick paper, thin aluminium foil, or gold 

 leaf be placed between the photographic plate and the film, the image is pro- 

 duced in the same way, and is sharply defined. If glass or mica be interposed, 

 the photographic plate is protected, and no image appears. We have been 

 unable to obtain glass or mica less than l-100th mm. in thickness. 



The film of latex may be heated to 200 C. without any diminution of its action 

 on the photographic plate. At this temperature it commences to char, and the 

 action on the photographic plate remains powerful despite the destruction of 

 the organic matter. When the ash becomes white, the action on the photo- 

 graphic plate is much lessened. The photographic effect is also obtained during 

 the passage of a dry air or of carbon dioxide, also under greatly reduced 

 pressure. 



Habitat. We do not know the original home of this plant, but we know 

 that from immemorial antiquity it has been known in Europe, Western 

 Asia, and North Africa. It has spread over most parts of the world, and it 

 is common in the coastal districts of most of the Australian States. It is a 

 weed of arable land and occurs on rubbish heaps everywhere. It would 

 appear to be difficult to break up land without the minute seeds of this 

 Spurge finding a lodgment, and covering the ground with its bright verdure. 



* H. G. Chapman, M.D., B.S., and J. M. Petrie, D.Sc., F.I.C. Report of the Australasian Association for 

 the Advancement of Science, Vol. XIII, 1912. 



