diff --git a/README.mdown b/README.mdown
index 8c54299..f44443b 100644
--- a/README.mdown
+++ b/README.mdown
@@ -365,7 +365,7 @@ This guide does not address these special requirements.
 I leave it up to you to research your mycelium species.
 
 [Grain spawn](#grain-spawn) is a common source of nutrients and the most accessible source of grain spawn is wild bird seed.
-You should, however, provide mycelium a variety of grain spawn and substrates between generations of colonies so the strain does not lose it's ability to digest different sources of nutrition.
+You should, however, provide mycelium a variety of grain spawn and [substrates](https://en.wikipedia.org/wiki/Substrate_(biology)) between generations of colonies so the strain does not lose it's ability to digest different sources of nutrition.
 
 These general instructions are the same for most grain spawn.
 
@@ -469,6 +469,7 @@ However, exposing more surface area give the mushrooms more room to sprout.
 - [ ] personal fan
 
 Coconut husk (coir) as casing layer and flooring in our fruiting chamber to hold moisture better than the mycelium cake we created in the [grain spawn](#grain-spawn) jar.
+It can also be mixed in with [grain spawn](#grain-spawn) for colonization as a substrate when changing the recipie between generations.
 
 0. Open and invert a fully colonized [grain spawn](#grain-spawn) jar and firmly but gently tap the mycelium cake out.