Xanthorrhoea grass trees in the Botanic gardens Melbourne

I photographed these two Xanthorrhoea grass trees in the Botanic gardens yesterday. They are both quite bizarre looking specimens. Another Xanthorrhoea tree known unfortunately by the common name 'black boy' is a favourite in Australian gardens and a very expensive plant. I bought one as a present for somebody once and the price was charged per cm of height! I think I paid about $80 for a plant only 20 cm tall. The ones below are not the 'black boy' types but are striking nonetheless.

This first one is called Xanthorrhoea malacophylla and is endemic to New South Wales. It is roughly 4 metres tall.

This last one is Xanthorrhoea quadragulata and is indigenous to South Australia. The top of the spikes are roughly 3 metres in height.