I suspect that you have one of the scale insects, very typical of this plant. The novice will have a difficult time recognizing scale insects since they are not mobile as adults, and are so small when young that they are not noticed.

Scale insects are busy sucking the plant's photosynthates into their own bodies. Excess is excreted in the form of sticky honeydew.

Scale insects are very difficult to get rid of on indoor plants, as there are very few systemic pesticides that are manufactured for indoor use. You must never use any product that is intended to be used OUTside on your house plants, unless you can keep the plant outside for several weeks.

If you have other houseplants, I would be willing to bet that you have methodically helped spread the scale from one to another so an investigation is in order.

What does this 'brown matter' look like? A brief description will help us determine whether or not it is the scale in question.

Here is a link that might be useful: Come on...let's learn about scale insects