MUTCAT_MYCUS

This is the easy part.  But now you know what I'm planning.
Increases effect of mass on vehicle speed.

Was doing testing for a road roller (uses ten roller drums for wheels) - experimented on a roller I've found (51' rollers, so wheel bigness was a constant, done on v12 engine), I was changing width (w) and mass (m) of the roller drum, while jotting down the safe/maximum speed (sp) that was attainable:
w=200, m=750 kg -> sp 33/1239
w=200, m=1500 kg -> sp 33/1239
w=200, m=15000 kg -> sp 33/1239

w=60, m=750 kg -> sp 95/1239
w=60, m=1500 kg -> sp 95/1239
w=60, m=15000 kg -> sp 94/1239
w=60, m=1 g -> sp 95/1239

w=20, m=750 kg -> sp 197/1239
w=20, m=1500 kg -> sp 197/1239
w=20, m=15000 kg -> sp 189/1239

While a v12 engine is powerful, being able to blast a roller weighing 150 000 000 grams (10*15 000kg in the most extreme case) at 189 km/h safely is a bit too much. That and the fact, that increasing total vehicle mass by a factor of ten lowered the safe speed by 8 hm/h (4%).
Plant marloss_seeds

Unfortunately no time for proper germination.
THRESH_MARLOSS->THRESH_MYCUS

Quite a lot of infrastructure, but now one should be able to get the
Mycus mutcat.  Still needs dreams, the actual mutation mechanics, and
all-important testing, but infrastructure is going up.  w00t.
nuke duplicate FLOWERS

Sorry, all.
Fix C&P glitch

Gagh.
Mycus skin/spawners

And the cleanup of a rather nasty F&R glitch.  Hoping I cured the merge
conflict here too.
Fix melee mal-fix

Hoping that was the only spot I mis-fixed.  Ugh.  Full branch corruption
like that isn't a joke.
WIP

OK, got nice-looking code that doesn't trigger.  Needs moved to
game::moninfo around 6033, committing to shift gears and go after a
showstopper reported in IRC.
Fixes and extra attack

OK, M_DEFENDER's adrenaline trigger seems to be working well enough, and
I've reinstated the Tower's tendril attack.  Gonna add more tendrils and
then this should be ready for checkover.
Tweaks, welcome, fixes, and dreams

Tweaks a few attacks and gets the tendrils to play nice if you've got
the other two Marloss mutations.  Adds some dreams to give people a
handle on the Mycus mentality.
Nail rogue bracket

:-/
update + scarred_zed

Incorporates i2amroy's at #9328--good catch--and adds beekeeper zeds to
the list of those protected from make_fungus.
Adds marloss tree

It's like a bush, but happens as a conversion chance when blossoms
fungalize a forest, and can on occasion regrow its fruit.  Thanks to
infectedmochi on the forums for the idea.
Sets peaceful to false when declining

Nice catch, Kevin.
The other side of mutagen-marloss interactions

Marloss rejects you if you've already breached.  Mutagens have a very
similar adverse reaction if you've opened the gateway.

BUT they just might be able to close it, too, if that's something you're
wanting.  Use wisely.
Mutation checkups

Locks in the traits.  The Mycus wants you to get them!
Adds prompters for Path Of Marloss

There's now a fairly tame addiction to prompt folks to seek out other
Marloss fruits, a comparatively-unlikely Marloss dream set, and the
Gateway pretty much tells you that the bush you wake up in is there
expressly for you.  (So examine the fungal thing!)
Changed crafting difficulty of some arrows

Changed Fabrication difficulty of Sharpened Metal Arrows, Heavy Fletched
Field Point Arrows, and Heavy Fletched Fire-Hardened Arrows from 5 to 4.

Previously, all components for heavy arrows were level 3, while all
heavy and metal arrows were level five, creating a gap in leveling
progress.   This update allows the improvised point heavy arrows to
serve as fabrication skill stepping stone.  Now archers don't have to
spend level 4 pointlessly grinding through unrelated recipes, but the
vastly superior Heavy Wooden and Metal arrows are still sought after.
actually fix the motel.