Have I drawn this Venn diagram correctly? Does this look correct?

http://i.imgur.com/vmlpYD8.png

I'm trying to find out whether this syllogism is valid (I'm guessing it's not valid)

Many thanks
The following argument is invalid:

(P1): All Cacti are Plants. (P2): Some Plants are Green. Conclusion: Some Cacti are not Green.

It's just that the non-Green plants needn't have any Cacti among them. The Venn diagram below illustrates that. Note that the diagram satisfies both (P1) and (P2), as required.
Statement 1: All cacti are plants implies that the cacti circle is 'in' the plant circle.
Statement 2: Some plants are green implies that there exist plants which are green. This may include the possibility of all plants turning green but excluding the possibility of 'not even one' plant which is not green. So, plant circle interaction with the green circle is 'non-zero'.
Statement 3: Some cacti are not green. You can never conclude this statement from the above two because there is no imformation of interaction of the cacti circle with the green circle.