Sunday, 8 January 2012

Notes on dissections for you all

I regard myself as lucky on this course, because I have done a year's worth of botanical taxonomy training... I kind of know what I am looking for when dissecting a flower. I know, for example that most flowers from the Rose family - Strawberry's, Roses, plums etc... have a hypanthium and I know the different types of arrangement in which the ovules can be arranged in an ovary. So before I go to Bali, I have loaded up some pictures from the best taxonomy book around with the hope that it will help all those who are doing dissections while I am away.

This is the book:


So we have all seen this type of diagram?


Good!

But there is so much more:

The diagram above shows you what it 'should' look like if there is a hypanthium present... The reason is starts as absent, then the hypanthuium appears and then goes absent again in the sequence is due to evolution... So you can end up with any of the 5 arrangements as shown above.


This shows how the gynoecium (female bit) can be arranged. The circles are transverse sections, the other longitudinal. As you can see, the ovules can be arranged in a number of ways in each locule (ovary). Along a column (axile), all around the edge (parietal), along one side of the edge (marginal) and sometimes several ovary's fuse to create a bigger septate ovary that has several cavities inside. Sometimes the axile placentation doesn't join at the top, and then it is called 'free central', and if there is only one ovule, then this can either be in the ovary as basal or apical depending on how it connects to the tissue.

This is how different anthers can empty themselves of pollen (dehiscence). Can be very important in dissections - especially in orchids.

Again, different dehiscence types on anthers.


Different arrangements of petals for a floral diagram




And - floral diagrams.. I find floral diagrams very easy to do and they can transform what is a very difficult flower to draw into a very easy one. This is for Julie so she understands what I was talking about on the cyclamen on the last comments in that post.


If you are donig a longitudinal section, you need to imagine what would be cut through the middle and what wouldn't be if you draw a line from the axis symbol all the way down the middle of that picture above to the bottom. When cutting a flower in two, you rarely get it straight down the middle, so you need this to refer to, plus the real flower in front of your to cross refernce with. I hope this helps.

3 comments:

  1. Blimey, the mind boggles! One for the library methinks. Enjoy Bali you lucky thing :)

    ReplyDelete
  2. Thanks Jess, definitely one for my library. Have a great time in Bali :)

    ReplyDelete
  3. Thanks so much Jess - good to have as reference and yet more to learn ... appreciate you posting this. Have a wonderful time in Bali - 3 more hours our way and you could pop in and say G'Day!!! :))))

    ReplyDelete