Private Blockchain – How to Send Transactions to a Private Network?

I have set up a private blockchain on a local network.
I have a node running on an Android smartphone and another on Windows 7, I use Geth on both.

I send Ether with the method eth.sendTransaction() from the Android node and I get a Tx Hash in result. Then I start the mining on the Windows node but the transaction is not added to any block.

I know that my nodes are connected because of the return of admin.peers() and the fact that I can transfer Ether if I send transactions from the mining node.

Is there something more to do for the mining node to see the transactions of the other node(s) ?

EDIT : the information of the nodes

To run the node on Windows :

geth --identity "ethRpi" --genesis "genesis.json" --rpc --rpcport "8080" --rpccorsdomain "*" --datadir "eth" --port "30303" --rpcapi "db,eth,net,web3" --networkid 2016 console

And on Android :

geth --ipcdisable --identity "ethRpi" --genesis genesis.json --fast --rpc --rpcport 8545 --rpcaddr 0.0.0.0 --port 30303 --rpcapi admin,db,eth,miner,net,personal,web3 --networkid 2016 --datadir=eth

On Android

>admin.peers
[{
    caps: [←[32m"eth/61"←[0m, ←[32m"eth/62"←[0m, ←[32m"eth/63"←[0m],
    id: ←[32m"efaa00ffc1d7955e97f4883d8497f4705520eca5a0f7ea63b3d2e2bcf9536fa0edd0cc2ebcf9974d6b2a90790491eefb351b0e135a61e8228f042c16d57d2df0"←[0m,
    name: ←[32m"Geth/v1.5.0-unstable-4f3f6e28/windows/go1.6.2/ethRpi"←[0m,
    network: {
      localAddress: ←[32m"192.168.68.111:30303"←[0m,
      remoteAddress: ←[32m"192.168.68.107:50740"←[0m
    },
    protocols: {
      eth: {
        difficulty: ←[31m9659008←[0m,
        head: ←[32m"163f33b0b9ba7c04cbef8e36796b6b2ef0bcb9af1fe1fa5be8fd05979cbcdc57"←[0m,
        version: ←[31m63←[0m
      }
    }
}]
>eth.pendingTransactions
[{
    blockHash: ←[1mnull←[0m,
    blockNumber: ←[1mnull←[0m,
    from: ←[32m"0xacc8770ed788bcb76fc14c570251585dd83925a8"←[0m,
    gas: ←[31m90000←[0m,
    gasPrice: ←[31m20000000000←[0m,
    hash: ←[32m"0x1d5ec2db286c52440b94e0d596467a15076c1a3ea2cb0995639d85677d051d69"←[0m,
    input: ←[32m"0x"←[0m,
    nonce: ←[31m0←[0m,
    to: ←[32m"0x52fa5791e401a4a33f045d5e34aea9976e5afd4f"←[0m,
    transactionIndex: ←[1mnull←[0m,
    value: ←[31m1000000000000000000←[0m
}]

On windows

> admin.peers
[{
    caps: ["eth/61", "eth/62", "eth/63"],
    id: "a7ae958bf83ad6c659567110abd8a15535a23acd66cd2ccc5bf2333b5f2b4a49a35e80450c9848e658b625b69078ab675882b51e44c17cea4c278746381c0447",
    name: "Geth/v1.5.0-unstable-4f3f6e28/android/go1.6.2/\"ethRpi\"",
    network: {
      localAddress: "192.168.68.107:50740",
      remoteAddress: "192.168.68.111:30303"
    },
    protocols: {
      eth: {
        difficulty: 9659008,
        head: "163f33b0b9ba7c04cbef8e36796b6b2ef0bcb9af1fe1fa5be8fd05979cbcdc57",
        version: 63
      }
    }
}]
> eth.pendingTransactions
[]
>miner.start()
I0628 09:54:58.658192 miner/miner.go:119] Starting mining operation (CPU=4 TOT=5)
I0628 09:54:58.660192 miner/worker.go:555] commit new work on block 74 with 0 txs & 0 uncles. Took 999.8µs
I0628 10:00:26.560682 miner/worker.go:337] ??  Mined block (#74 / 0bebfb50). Wait 5 blocks for confirmatio
I0628 10:00:26.562682 miner/worker.go:555] commit new work on block 75 with 0 txs & 0 uncles. Took 999.9µs
I0628 10:00:26.562682 miner/worker.go:555] commit new work on block 75 with 0 txs & 0 uncles. Took 0
I0628 10:00:26.608677 miner/worker.go:337] ??  Mined stale block (#74 / 0bd0e716).
I0628 10:00:26.647674 miner/worker.go:555] commit new work on block 75 with 0 txs & 0 uncles. Took 0
I0628 10:00:29.670371 miner/worker.go:337] ??  Mined block (#74 / cd692c59). Wait 5 blocks for confirmation
I0628 10:00:29.671371 miner/worker.go:555] commit new work on block 75 with 0 txs & 0 uncles. Took 0
I0628 10:00:29.687370 miner/worker.go:337] ??  Mined block (#74 / c082d521). Wait 5 blocks for confirmation
I0628 10:00:29.688369 miner/worker.go:555] commit new work on block 75 with 0 txs & 0 uncles. Took 0
I0628 10:00:29.703368 miner/worker.go:555] commit new work on block 75 with 0 txs & 0 uncles. Took 0
I0628 10:00:31.953143 miner/worker.go:337] ??  Mined block (#75 / 542384a4). Wait 5 blocks for confirmation
I0628 10:00:35.181820 miner/worker.go:555] commit new work on block 76 with 0 txs & 2 uncles. Took 8.9991ms
I0628 10:00:35.183820 miner/worker.go:555] commit new work on block 76 with 0 txs & 2 uncles. Took 999.9µs
I0628 10:00:35.185820 miner/worker.go:555] commit new work on block 76 with 0 txs & 2 uncles. Took 0
I0628 10:00:39.623376 miner/worker.go:337] ??  Mined block (#76 / 18796f50). Wait 5 blocks for confirmation
I0628 10:00:39.743364 miner/worker.go:555] commit new work on block 77 with 0 txs & 0 uncles. Took 999.9µs
I0628 10:00:39.750363 miner/worker.go:555] commit new work on block 77 with 0 txs & 0 uncles. Took 0
I0628 10:00:42.795059 miner/worker.go:337] ??  Mined block (#77 / 651df4a0). Wait 5 blocks for confirmation
I0628 10:00:42.796059 miner/worker.go:555] commit new work on block 78 with 0 txs & 0 uncles. Took 999.9µs
I0628 10:00:42.815057 miner/worker.go:555] commit new work on block 78 with 0 txs & 0 uncles. Took 0
I0628 10:00:43.384000 miner/worker.go:337] ??  Mined block (#78 / 021c7f6a). Wait 5 blocks for confirmation
I0628 10:00:43.400998 miner/worker.go:555] commit new work on block 79 with 0 txs & 0 uncles. Took 0
I0628 10:00:43.444994 miner/worker.go:555] commit new work on block 79 with 0 txs & 0 uncles. Took 0
mI0628 10:00:43.923946 miner/worker.go:337] ??  Mined block (#79 / 8eef4802). Wait 5 blocks for confirmation