Botany marches on – Part 1, basal angiosperms and monocots

April 13, 2010

Warning! I’m going to get into some detailed botany here, so if you are not deeply into the flowering plants and their classification and you do not own my book, A Tour of the Flowering Plants, you may not wish to wade through all this. It is basically for advanced elementary and secondary Montessori botany studies and for anyone else that owns the book. A Tour of the Flowering Plants is still quite useful to show the appearance of angiosperm families, whether or not you are concerned about the latest classification.

Last fall, the Angiosperm Phylogeny Group published a third report concerning the classification of the orders and families of flowering plants. The report, published in the Botanical Journal of the Linnean Society, is called APG III. There is a summary of APG III on Wikipedia. http://en.wikipedia.org/wiki/APG_III_system My book, A Tour of the Flowering Plants, is based on the 2003 report from this group, which is called APG II. The book has some further advances that were published on the Angiosperm Phylogeny Website of Peter Stevens. http://www.mobot.org/MOBOT/Research/APweb/welcome.html

I’ll go over the APG III changes, beginning with this post. If you own my book, you can decide if you want to add notes to it. You may contact me via my website (www.bigpicturescience.biz) if you would like a list of the pages and changes for bringing A Tour of the Flowering Plants in line with APG III.

Will the changes keep coming over the years as we acquire more and more DNA data? I think that future changes will be modest and will not affect the general structure of the angiosperm tree. There aren’t that many unplaced groups left. There will likely be little surprises, like one I give below for Nymphaeales.   

For now, let’s start with the first branches of the angiosperms, grouped as the basal angiosperms in A Tour of the Flowering Plants. The Nymphaeales got another family, Hydatellaceae, which was formerly placed in the grasses. This shows how much DNA studies can reveal, and what studies of morphology may not be able to distinguish. This family is tiny, both in size and numbers of species. The only reason I mention it is the idea that when plants adapt to living in water (or any other extreme environment), they often change form so much that they don’t resemble even their closer relatives. You can see the plant here: http://www.ubcbotanicalgarden.org/potd/2007/03/hydatellaceae_1.php

The order Chloranthales was previously unplaced – no one was sure what its closest relatives are. Now it is considered to be a sister group to the magnoliids. The magnoliids themselves have not changed in APG III. This branch of the flowering plants includes the laurel and black pepper families, as well as the magnolias. Although their seeds have two cotyledons, they are not closely related to the eudicots. The eudicots are the traditional dicots minus the magnoliids and the basal angiosperm lineages.

In A Tour of the Flowering Plants, I used terms for branches of monocots that have since disappeared. You don’t have to worry about whether to call the Liliales and Asparagales “lilioid monocots” or “petaloid monocots.” Just call them monocots and go on. The only lineage of monocots that gets a special name now is the commelinids. “Lilioid” and “petaloid” should be understood as informal terms that refer to plants that were traditionally lumped in the lily family. Most of them have large, showy tepals.

The major change in the monocot is the grouping of several small families as subfamilies under the enlarged families Amaryllidaceae, Asparagaceae, and Xanthorrhoeaceae. This is all within the order Asparagales. Here’s the breakdown:

The enlarged Amaryllidaceae has the agapanthus subfamily (Agapanthoideae, equivalent to the former Agapanthaceae), the onion subfamily (Alliodeae, equivalent to the former Alliaceae), as well as the amaryllis subfamily (Amaryllidoideae, equivalent to the former Amaryllidaceae). The members of this enlarged family have their flowers in umbels that are enclosed by two bracts when the flowers are in bud.

The enlarged Asparagaceae is really big. It has the Brodiaea subfamily (Brodiaeoideae), the scilla subfamily (Scilloideae, which includes the former hyacinth family, as the tribe Hyacintheae), the agave subfamily (Agavoideae, which includes the former Agavaceae), the Nolina subfamily (Nolinoideae, equivalent to the former Ruscaceae), as well as the asparagus subfamily (Asparagoideae). Yet another subfamily holds several Australasian species such as the cabbage tree, Cordyline.  

Asparagaceae members have flowers in racemes or in umbels that have three or more bracts at their base. The umbels, if present, do not have the pair of enclosing bracts seen in Amaryllidaceae.

The enlarged Xanthorrhoeaceae (the grass tree family) includes the daylily subfamily (Hemerocallidoideae) and the asphodel subfamily (Asphodeloideae), as well as the grass-tree subfamily. I did not include the grass tree family in A Tour of the Flowering Plants because it is native to Australia and not commonly used in North American landscaping.

The cattail family, Typhaceae, got a second genus, Sparganium, the bur-reeds. It’s not hard to see these two aquatics as relatives.

I’ll address the APG III changes to the eudicots in another post.


New Plant Kingdom ideas & new cards and chart

March 23, 2009

sori-leaf2
Sori on the leaf of a leptosporangiate fern

I recently revised my photo cards for the plant kingdom. They were previously called “Phyla of the Plant Kingdom.” With most of the phyla no longer being used, the title had to change. Now that set is called “Major Branches of the Plant Kingdom.” It still has 40 cards and each card still carries the classification on the back, but there have been changes to the text. I also put in some new photos, such as the one for the leptosporangiate ferns. There are new clearer photos for some of the mosses and club mosses. I’ve combined some illustrations onto one card and added two new families of conifers, the juniper/redwood family, Cupressaceae and the yew family, Taxaceae.

If you are introducing the plant kingdom to elementary students, I recommend the revised Plant Kingdom chart from InPrint for Children. http://www.inprintforchildren.com/store/  Carolyn Jones has done her usual high quality design job and added color to the individual illustration cards that go with the chart. Please note that she is closing retail sales soon, but her charts will be available from Montessori Services. http://www.montessoriservices.com/store/

New Plant Kingdom chart from InPrint for Children

New Plant Kingdom chart from InPrint for Children

I’d like to go back and make one more stab at explaining the changing view of the plant kingdom. The bryophytes still have phylum names, so I listed them on my cards, but it would be perfectly OK for precollege levels to simply call them by their common names – liverworts, hornworts, and mosses. These three lineages are monophyletic (“one lineage”) and they have a similar type of life cycle and yet it isn’t totally clear if they share a recent common ancestor. They could be shown on a separate branch or as three separate branches coming from the plant kingdom before the vascular plants branch off.

The first branch of the vascular plants is the lycophytes. If they are a phylum, then the other phylum would have to the euphyllophytes (“true leaf plants”), which is both the monilophytes (fern lineages) and the seed plants. If the fern lineages were to have phyla, there would have to be one for the whisk ferns and the ophioglossid ferns (adder’s tongue and grape ferns), one for the horsetails, one for an obscure group of tropical ferns, and one for the leptosporangiate ferns. The seed plants could have phyla for the gymnosperms and angiosperms or for each of the major seed plant lineages or??? More data is needed, but maybe it is just time to discard phyla for the plants. The view of the full lineage for each group is a much richer view.