OK 1st pass—nitpicks:    

 *lead could be longer, especially more information about what it looks like. Link fungus, mushroom, birch; floor -> ground, or forest floor 
 *taxobox width to 234 px? (I guess I'm foisting my personal preferences here, but I think it looks neater when the taxobox width is the same as the mycomorphbox) 
 *synonyms ref and synonyms in taxobox? Mention Galorrheus vietus and Lactifluus vietus in taxonomy 
 *Russulales News is well-respected for info about species in that order, and has further taxonomic synonyms 
 *link "first described" to species description 
 *Systema mycologicum and Epicrisis systematis mycologici are both on Google books (and Biodiversity Heritage Library), so you can cite these publications directly 
 *"L. vietus typically" No abbr to start para 
 *"(0.98 to 3.0 in)" suggest reducing convert template output to 1 decimal place, it's just an approximation anyway, based on a small sample size (other instances later) 
 *link umbo 
 *I like to replace jargony "incurved" with "curved inwards" or similar 
 *link buff, adnate, decurrent, flesh 
 *"lemellulae (gills that do not reach the cap margin)" -> "lamellulae (short gills that do not reach the stem from the cap margin)" 
 *"which dries as a brownish or greenish grey" 
 *link spore print 
 *"amyloid (staining blue in iodine)" Melzer's reagent is more than just iodine, so probably better to use the reagent name; could also link staining 
 *"well developed" needs hyphen 
 *"measuring between 8 and 9.5 by between 6.5 to 7.5" second between unnecessary, it's implied; there's a couple later as well that can be removed 
 *"The pleurocystidia (cystidia on the edge of the face of the gills)" 
 *"narrow spindle" -> spindles 
 *4-spored -> four-spored per MOS 
 *"and the mushroom as a whole lacks a distinctive smell." 
 *"L. vietus is fairly common" no abbr 
 *link conifer, hardwood 
 *any more details about the distribution? Europe and North America are big places… 
 *Refs: title case for books, sentence case for journal titles; endashes for page ranges; need page #'s for Trappe 1962; author format for ref #14 is different than the rest