Most of the plant juices flow through the outer part of the stem, in the layer just under the "bark", called the phloem...(pronounced flow-um)
That's why if you break a branch off, and some of the "skin" is still attached, the branch stands a good chance of surviving- if there's none of that outer layer still connected to the broken branch, just throw it away, because it's as good as dead...
She's probably right...in fact, Mrs.C.
may have mentioned the same thing a time or two...
But for a Californian, not so much..
And this is to put your mind at ease a little more about the hollow stem thing, Trala- this is the stem(s) from my Blackberry...notice they're
all hollow...