Tree texture assets missing in unity 2018.2.6f1

I am following the tutorial at

file:///Applications/Unity/Documentation/en/Manual/tree-FirstTree.html

under section ’ Adding Materials’ do not see the texture assets such as “BigTree_bark_diffuse” for the Base and Gloss properties, and “BigTree_bark_normal”.,

You can find these in the “Standard Assets” package in the Unity Asset Store.