This statement must be considered in the context of the essay written by Bacon, Of Studies. In the essay, Bacon is discussing what studies are for, or should be for, and how to best use them to improve oneself. The statement you have isolated is:
They perfect nature, and are perfected by experience: for natural abilities are like natural plants, that need pruning, by study; and studies themselves do give forth directions too much at large, except they be bounded in by experience.
In this part, Bacon is saying that studies are wonderful if they are also combined with experience. If one is only to rely one’s study of a subject, then one is merely a theorist. Studies should be combined with experience to truly be worthwhile. Studies can point us in the right direction, but the directions can be too broad (too much at large). It is only when we combine studies with experience that we make the best use of both – study and practicum. Think of it as being a doctor. You have to go to Med school and study the theories, but would you want a doctor that had only medical theory and no practice?