I squat with 135 lb 15 reps. What would be the result, as far as the appearance of my legs, if I keep it at 135 lb and gradually increase the reps to 100? I know it may take awhile. (don't want huge legs)

if your doin 100 reps your legs will be pretty big.

Well, first and foremost, make sure you're squatting properly (you can learn how to do that here: http://www.youtube.com/watch?v=Kp4zZmVc2nQ). Because if you're planning to do 100 squats, and you're not doing them 100% correctly, you'll hurt your knees or lower back or something else. Second of all, DO NOT do sets of 100 squats. That is a surefire way to bulk up your legs. If you truly want to tone, in my experience (I was selected as one of the top 5 personal trainers in Toronto), you want to squat heavy, but for low reps and low sets. So if you continually increase the weight of your squats, and do 2 sets of 5 reps or less, just 1-2 times per week, you'll develop strength without size. Case in point, look at the weightlifters and powerlifters in lower weight classes (we're not talking about the big guys, who have no limit on how much they can weigh). We're talking about the guys who weigh only 132 pounds, yet lift close to 400 pounds. Think they have big legs? Well no, they can't possibly have big legs at 132 pounds. But you can bet that they have strong and toned legs.