1.) I had been wishing to identify a plant and I think a helpful gardener in Victoria has assisted me. I believe it is in the genus Euphorbia and is specifically one of the following:
http://en.wikipedia.org/wiki/Euphorbia_cyparissias
http://en.wikipedia.org/wiki/Euphorbia_amygdaloides
http://en.wikipedia.org/wiki/Euphorbia_esula
http://en.wikipedia.org/wiki/Euphorbia_helioscopia
http://en.wikipedia.org/wiki/Euphorbia_peplus

The common name "spurge" derives from the Middle English/Old French espurge ("to purge"), due to the use of the plants sap as a purgative.

from http://en.wikipedia.org/wiki/Euphorbia

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2.) The latex (milky sap) of spurges acts as a deterrent for herbivores as well as a wound healer. Usually it is white, but in rare cases (e.g. E. abdelkuri) yellow. As it is under pressure, it runs out from the slightest wound and congeals within a few minutes of contact with the air. Among the component parts are many di- or tri-terpen esters, which can vary in composition according to species, and in some cases the variant may be typical of that species. The terpen ester composition determines how caustic and irritating to the skin it is. In contact with mucous membranes (eyes, nose, mouth) the latex can produce extremely painful inflammation. In experiments with animals it was found that the terpen ester resiniferatoxin had an irritating effect 10,000 to 100,000 times stronger than capsaicin, the "hot" substance found in chillies. Several terpen esters are also known to be carcinogenic.
(my emphasis)

from http://en.wikipedia.org/wiki/Euphorbia#Toxicity

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3.) (As a sidenote, the following are also in the genus Euphorbia:)

http://en.wikipedia.org/wiki/Image:E_meloformis_valida_ies.jpg
http://en.wikipedia.org/wiki/Image:Weihnachtsstern_-_gro%C3%9F.jpg
http://en.wikipedia.org/wiki/Image:E_actinoclada_ies.jpg

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