Canes are made by "bundling" together all the different colours in the desired pattern in a great big block - so that it's sort of like a stick of Blackpool rock, with the pattern running through it. It's then heated to fuse it all together, then, at the right time, it is very quickly pulled out to stretch it, like toffee, and the pattern becomes small. I think there may be more efficient ways of doing it now, but it used to involve the glassmakers running away with one end of it!
The thin sticks (like thin Blackpool rock) are then cut into tiny sections - each of which is used individually.
In a bit like this, thin sections of cane have been marvered onto the surface of the hot gather of clear glass, then it has been further blown, which stretches the cane slices out and incorporates them with the body.