The website is back online and seems to be functionally normally.
If you did not see part 1 of this post, please take a look at its first paragraph. This post is more on the fall 2009 publication by the Angiosperm Phylogeny Group, the report called APG III. What I’m giving here is how APG III differs from my book, A Tour of the Flowering Plants. This post is primarily for Montessori botany studies and general learners that own my book. (And if you are interested in acquiring A Tour of the Flowering Plants, see www.bigpicturescience.biz.)
The changes in the eudicots include the assignment of Geraniales and Myrtales to the malvids (eurosids II) branch of rosids. These two orders were previously found to be within the rosids, but their exact location was not clear. Now they are sister lineages that branch near the base of the malvids.
Caryophyllales is listed before the asterids, while the Saxifragales is listed before the rosids. This is the way I depicted these lineages on the informal tree diagram in my book, A Tour of the Flowering Plants. The former Caryophyllales family, Portulacaceae, has been divided, as it held several not-closely-related genera. The genera Claytonia, Montia, and Lewisia have been moved to the new family, Montiaceae.
Lastly the Dipsacales order (in the campanulids or euasterids II branch of the asterids) has had several former families combined into an expanded Caprifoliaceae. The twin flower family – Linnaeaceae, the valerian family – Valerianaceae, the teasel family – Dipsacaceae, and the bush honeysuckle family – Diervillaceae have all become part of Caprifoliaceae. This leaves Dipsacales with only two families, Adoxaceae and Caprifoliaceae.
There have been a number of adjustments in smaller families that are not common in temperate North America. I view these as tweaking the twigs, not establishing the branches. All-in-all, the bulk of the APG scheme has been reaffirmed in the last several years.
What difference do all these changes make? Unless you are an editor of scientific papers, it isn’t absolutely necessary to learn the minor adjustments to the APG scheme. The main thing that students need is the phylogenetic view of life and of the angiosperms. If they see these plants as descendents of a common ancestor and know the major lineages, that’s good. Some may want to delve deeper and that should be encouraged. Mabberley’s Plant Book: A portable dictionary of plants, their classification, and uses (third edition, 2008) by D. J. Mabberley is a valuable reference for further study and to help sort out the changes.
How does the Angiosperm Phylogeny Group classification affect horticulture and native plant identification? I can more easily answer when it will affect these two – that will be over a period of time. Field manuals aren’t going to be re-written overnight and horticultural labels frequently lag behind academic classification. Nonetheless, I think that phylogenetic classification will eventually take over. It certainly makes more sense to focus on the APG scheme and look to the future if you want to address plant classification.
A major goal of Montessori botany studies is to help children learn to observe and understand plant structures. There are a lot of things going on in the plant world that take a sharp eye and careful observation to find. The life cycle of pines is one of them. It is important for the teacher/guide to show children inconspicuous plant structures such as pine cones throughout the year and explain to them what is happening.
Most people are familiar with conifer cones, although they tend to call all of them “pine cones.” Few have followed the development of a cone through the year – or two years in the case of pines – that it takes for a cone to mature. I have been photographing the development of pine cones and here’s a look at their life cycle.
Pines have two kinds of cones on the same tree, pollen cones and seed cones. The latter are formally called ovulate cones. The trees don’t usually form cones every year. In cone years, the cycle begins as the new shoots elongate in the spring. The seed cones form at the end of the new growth. They look like tiny pink-to-purple bristles.
The pollen cones cluster at the base of the new shoots, beneath the terminal bud. Most of the pollen cones form on the lower branches of the tree, away from the seed cones, but sometimes they form on the same shoot as the seed cones. The wind usually won’t take pollen from the base of the tree to its upper branches, so the arrangement of seed and pollen cones encourages cross-pollination.
Conifers use wind pollination, which requires a lot of pollen to work, and in cone years the trees produce an amazing amount of pollen. Pollen cones tremendously outnumber seed cones. After they release their pollen, most of the spent pollen cones drop off the tree. You can sometimes find dried ones in the branches later in the summer, however.
It takes careful observation to find the budding ovulate cones, even though they can be colorful. They hide among the new needles and are most easily seen from above, the bird’s eye view we don’t usually have. It doesn’t help that the ovulate cones usually form on the higher branches. You may need to pull a branch down so that the children can see the tiny new cones. The little cones of pines don’t grow much during their first year. In the fall, they have become browner and drier looking, but are nearly the same size as they were in the spring.
In the second spring the pine seed cones rapidly enlarge. A shoot I photographed had a pair of seed cones, but one of them had died. It provides a size scale to show how much the live cone has grown. Fertilization is a slow process in pines. It takes about 15 months for the egg cells to form and the pollen tube to grow and deliver the sperm to the eggs. The scales of the seed cones are green until late fall. By that time the seeds are mature. The cone dries and the scales spread apart, releasing the winged seeds. The dried cone may remain on the tree for months or years, until a strong wind brings it down.
In case you need help finding your local pines, look for a conifer tree with needles in bundles of two to five. Other conifers, such as firs or spruces bear their needles singly. Their cones mature in one year, but they can be even harder to see because the seed cones form in the tops of the tree.
Take a look around this spring and see if you can locate some young cones to show your children and to follow through the cone life cycle.
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/
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.
Welcome to Priscilla’s blog. Check here often for news about upcoming new science learning materials, freebies, discussion of science teaching methods, and more.
Visit http://www.bigpicturescience.biz to learn about innovative and up-to-date science education materials.