Julius von Sachs (1832–1897) was a German botanist who developed a lot of thinking around plant physiology. This blog summarises (in my words) his writings on mistletoes from lectures written in 1887:

Aerial roots
Can be regarded as ordinary roots that are prevented from normal development by accidental circumstances. They are capable, when presented with soil, of growing into normal long, branched roots. These roots often remain short and simple when growing without soil. 

Haustoria
Parasites have degraded root systems that "lose their ordinary typical structure, and at last only amorphous masses of tissues or even isolated cells remain". Haustoria only have in common with normal roots the fact that they penetrate substratum to absorb food. 

Mistletoe (referring to Viscum species)
Mistletoes produce organic materials independently of the host tree with no lack of chlorophyll as even the fleshy roots within the host tree are green in colour. Parasitism by mistletoes is only partial and therefore so is the degradation for the host tree. 

Germination and growth
When a viscid fruit sticks to a young tree branch, the large embryo, very rich in chlorophyll, germinates and its root tips turns away from the light, toward the host branch. The radicle bores through the cortex and cambium into the host wood. From these very active roots spring new shoots which break through the cortex of the host branch, come forth into the light and from these, new roots again run into the cortex. Occasionally, an entire tree, from crown to root, is infested with the mistletoe.

So there you go, the study of these interesting plants has been happening for a long time!

We've made some interesting epiphyte finds during recent outdoor adventures that you might be interested in:

Kauaeranga Valley, Coromandel

On a mission to find Metrosideros albiflora we also found large puka (Griselinia lucida), Phlegmariurus varius, blankets of filmy ferns (Hymenophyllum species) and huge matua mauku (Hymenophyllum dilatatum).

Five minutes before it was time to turn back we found the wonderful, large-leaved aka (Metrosideros albiflora). It has the largest leaves and flowers of the aka/climbing rata that left us with no doubt that we had found the right species!

Atuanui/Mt Auckland

This maunga/mountain is 22 km north of Kaukapakapa, in Northland. It is an important place for Ngāti Whātua and, at 305 metres above sea level, is the highest peak in the district. This is an interesting landmark that I've driven past far too many times. Well worth the stop, it is a nice example of northern NZ rainforest that is dominated by huge pūriri (Vitex lucens) and beautiful taraire (Beilschmiedia tarairi).

Interesting epiphyte finds at Atuanui included large puka (Griselinia lucida) (again), huge nest epiphytes (these ones were Collospermum hastatum) clinging to skinny  nīkau (Rhopalostylis sapida) and the uncommon tāwhiri karo (Pittosporum cornifolium).

Rangitoto Island

This wonderful pest-free reserve once again provided some exciting epiphyte finds. The flowering kohurangi (Brachyglottis kirkii var. kirkii) were a highlight with their bright white displays brightening up the dark lava around them. We also found the whisk fern (Psilotum nudum) and lovely little taupeka (Notogrammitis heterophylla).

It is a marvellous time of year to explore our natural areas so get out there and look for your local epiphytes!

As discussed in the Medicinal Mistletoes blog post, mistletoe species belonging to the genus Viscum have been shown or speculated to have a range of medicinal values. Extracts of Viscum species have been used to treat cancer, diabetes, and dementia and control immune system responses. Following on from the known traditional uses and recent scientific findings, Shin-Hae Lee and colleagues have recently discovered that extracts from a Korean mistletoe (Viscum album subsp. coloratum) can extend the lifespan of worms and flies.

To process the mistletoe for their study, these researchers mashed leaves from local plants that were growing on oak trees and then boiled them for 3 hours in water before using centrifuging and filtering the material. This was then added to the food of Drosophila melanogaster fruit flies and applied to the agar plates that Caenorhabditis elegans worms were living in.

During the experiment, the researchers measured lifespan and various stress and performance variables of both species. They found that the mistletoe extract successfully extended the lifespan of both the flies and worms. 

The following graph shows the survival rate over time for the worms. The dotted and dashed lines are populations treated with KME (Korean Mistletoe Extract) and you can see that the populations that received both the low and high KME doses outlived the control population:

This research is likely to lead to more work in the area of mistletoe medicine and lifespan longevity because there are many complicating factors that are not yet understood (check out the article if you're interested in the details).

Some of New Zealand's mistletoes are in the same family as Viscum album but as mentioned in this post, they are not known to have medicinal properties. 

Just throwing it out there: 
I want to do this in New Zealand...

I realise that photographing an entire tree requires super expensive and tricky equipment but I'm keen to make a more basic attempt and who knows, it might lead to something closer to nat. geo. standards. Any of the great southern beeches, enormous Pureora miro or laden Waitakere rata would make perfect stars. Does anyone have ideas for making this happen? Here is a video explaining how the professionals get it done:

The reasons behind my desire to give this a go in New Zealand are:

1. as far as I am aware, it has not yet been done here
   
2. it would be a marvellous way to document the diversity and complexity of a tree habitat
   
3. people would find it interesting and engaging
4. it would be lots of fun!

So, if you're a photographer, tree climber, kind person willing to fund hairbrained ideas and/or keen epiphyter and you want in, let me know!

Finally, and on a slightly different topic, have a look at this beautiful blog by Dylan van Winkel that features epiphytic flora and fauna from Hauturu/Little Barrier Island.