Various cacti identification help

[ElieEstephane]

Hello everyone,
This is my first post but i've been a fan for a while. I own many cacti and succulents. However, these remain nameless.
First off, the mammillaria. I bought it labelled as mammillaria. It had yellow flower buds and 4 spikes one of which is prominent as shown in the pictures. The spines are brownish and it has a clumping nature. The closest i could come close to is mammillaria gigantea.
Cacti 1 2 and 3 are a roadside find and i would really love to id them because i woukd like to buy more of them. Only cactus 3 has respectable roots. Cacti 1 and 2 barely have any roots. It is winter in here so im keeping them dry in a cold dark room. I really like cacti 1 and 2 and i want to help them recover. Im thinking about cutting the base in the spring and rooting them. Is this advisable? And how deep would i have to place them to root them? They're about 2 to 3".
Many thanks in advance.

[Kamos]

The last one looks like Mammillaria karwinskiana.

[ElieEstephane]

The last one looks like Mammillaria karwinskiana.

Could very well be but i saw it has more spines per node and lacking the dark spines. I browsed through the whole mammillaria catalogue and didnt find a satisfying answer.
But many thanks to you!

[george76904]

I would agree with Kamos, it appears to be mammillaria karwinskiana, individuals can show great variety in spination. Even though cacti guide may show them slightly different populations in habitat often vary greatly, and usually only a few populations are observed to define a species. Therefore my money would be on mammillaria karwinskiana.number one appears to be an echibopsis or trichocereus hybrid, numbers 2 and 3 are both mammillaria. I would say that there is no need to reroot them, they already have roots and will grow more when they get proper growing conditions.
Hope this helps,
Will

[greenknight]

Put them in pots only a little larger than their root balls, otherwise the soil tends to stay wet too long. Since they might not fit a pot that small, be too top-heavy, you can use larger pots and put some rocks in to take up the extra space. Good-size rocks, not a layer of gravel which actually interferes with drainage - http://gardening.stackexchange.com/ques ... ater-table

Make sure the potting mix gets down between the rocks to create drainage channels. I've used this method very successfully.

The first 3 I would class as rescues, you saved them from a sad fate. The 4th is a good-looking plant - and I agree with the ID of M. karwinskiana.