Engine Part on 1995 Subaru Impreza

I have a 1995 Subaru Impreza L Wagon with the 2.2 liter engine, AWD and an automatic transmission. I am getting the car fixed up and notice a cracked part in the engine. Before I bring it to a mechanic, I wanted to know what the part was. It's on the bottom of the engine compartment, on the left side (if you are facing the vehicle from the front, in other words, on the passenger side), at the part of the engine nearest the windshield.

I have attached a link to a picture of the part. If anyone can tell me what it is, I'd greatly appreciate it. As you can see, there is a green cylinder and a plunger like part attached to it.

http://www.flickr.com/photos/23905496@N03/2275794926/


http://www.flickr.com/photos/23905496@N03/2275794926/

thats an axle

So, which part was cracked?

the boot. if you are in a money crunch you could theoretically wait until the axle starts clicking around turns, but generally once the boot breaks its about time to replace the axle. if you catch it right away, the same day the boot breaks, you could regrease and reboot it but thats sort of a tossup whether it will last or not. sometimes it does and sometimes it wont.