In microscopes you have a magnification in the ocular (small magnification eg. 5 or 10x) and another one in the objective lens (eg. 10, 25 or 100x). For a magnification of 1000x (ocular 10x and objective 100x) you’ll need imersion oil to put on the slide (oil has better refractive index for this). If you want to see germination in pollen you don’t need imersion. But once you are working with a microscope and use it for other things as well you’d might want to have the maximum magnification.
From my personal experience using microscopes at school, the oil imersion lense is rarely used. As Leen said, you won’t need it to look a pollen germination, and I wouldn’t think you’d want it for root tip squashes either, if you want to figure out ploidy – so, unless you are planning at looking at VERY small things, you probably don’t need to invest in it – and I’m assuming you could always buy one later if you find that you do want higher magnification after all.
Joan, you may want to look at the after Christmas sales for top of the line “toy” microscopes. We have purchased them for grandchildren and they seem to be good.
Can anyone else comment on these “toys”?