Let us now go to the flowering plants or what we call the angiosperms which I already described as uh literally meaning "container seeds," 250,000 plus species probably closer now to probably 300,000, especially in molecular biology where we're uh dividing and subdividing different forms into different species and that sort of thing and we're discovering new things, two big groups: the Monocots and the Eudicots, uh obviously everybody knows about flowering plants using various pollinators insects and that sort of thing to transfer pollen uh you're less dependent on wind, you have less pollination, these are the most advanced the most sophisticated of the of the plants you're not having obviously pollen dispersed by the wind, now you've got pollinators being attracted by flowers right and uh pollinating much more precise okay? The clearly the flower is the defining reproductive adaptation of of angiosperms um the two big points about angiosperms is flower and fruit and we're going to see the fruit in a minute the flower for attracting pollinators of the fruit for uh seed dispersal if you smell good and you taste good the animals will eat you and you'll get the seeds dispersed, hence the importance of fruit. I will hold you to the parts of the flower. Again here we go with stamen there's the male, carpel or I'm fine we've already presented the term pistil, pistil or carpel will work okay and again uh when we talk about the stamen we've got the anther and the filament when we talk about the pistol or carpal you've got the stigma the style and the ovary, and again when you take a look at this you see the sepal is responsible for protecting and closing the bud petals a sterile non-reproductive parts obviously we know petals attract pollinators uh the stamen produces the pollen, uh the pistil AKA carpel literally evolved from a seed bearing leaf that was rolled into a tube the stick stigma is interesting that receives the pollen it's sticky uh when they go to get a little nip of nectar the pollinators that sticky stigma is going to attract obviously uh the the pollen grains and they're going to stick there and the ovary protects the ovules and you know I you know for the 10th time the ovules will ultimately develop into seeds upon fertilization. We've already talked about fruit dispersing the seeds, again a fruit is nothing more than a ripened ovary and we're going to talk about that in more uh detail, uh aggregate fruits several ovaries that are part of the same flower, an example would be a raspberry multiple fruit uh in this case one that develops from several uh separate flowers so if you look at a pineapple, there's literally a cluster of flowers and basically uh each one of those flowers is going to become like a little fruitlet and ultimately produce what we know as a pineapple it's called a multiple fruit. We know about seed dispersal, walk out into the woods and you've got some of the ones from uh the maples coming down like propeller helicopters and you've got some of the uh ones with with burrs on them that get stuck to animal fur and your shoes and that sort of thing as a means of dispersal, uh this is an interesting one about edible fruit, many times these fruit have got these seeds in them that's hard and shiny and uh unless we had a rhinoceros back at the greenhouse they would not germinate, so a lot of times we have to nick them or put a scar in the seed in order to get them to germinate and uh in in horticulture we call it scarifying to scarify a seed means to nick it to put a scar there cuz normally there out in the wild you would have herbivores and these seeds would pass through the GI tract of a herbivore, rhinoceros, elephant, that sort of thing, and they would obviously uh be processed that way, okay? Again so when you look at the life cycle of uh of of a flowering plants, of angiosperms again it's a typical alternation of generations let's not forget that the dominant generation is the sporophyte generation, heterosporous like all other uh seed plants you should know about microsporangia and megasporangia, and again know your gametophytes, notice I say here the immature male gametophytes are pollen grains, so the question is that what's the what's the mature male gametophyte? Here's a pollen grain of Pinus right that would be an immature uh gametophyte. Now if we added the pollen tube, that would be the mature uh male gametophyte, but pollen grains obviously we've already talked about they develop in the uh within the anthers of the stamens again each pollen grain is going to have two haploid nuclei right they're going to have the two haploid nuclei uh that are going to participate in double fertilization, if I ask you what is the the the salient characteristic, the main characteristic of um uh angiosperms, it is what we refer to as double fertilization which we are going to talk about. Again keeping with the theme of knowing what's the male gametophyte, what's the female gametophytes, female gametophytes do not produce an archegonium, they're located within the ovule and again uh we're talking about they consist of only a few cells, an embryo sac, that is the female gametophyte, uh eight haploid nuclei in seven cells that means there's a a situation where there is a central cell that contains two haploid nuclei so female gametophyte, that is the the uh the embryo sac, one of the eggs obviously one of the cells is going to be the egg okay, so let's take a look at this and again I'm not going to read uh the description that verbal description is for you I would rather use pictorial representation and again here's the mature flower on the sporophyte plant and again diploid and again we're showing obviously anther and carpel uh again you've got your microsporangium producing microspores that ultimately are going to produce pollen grains, notice what it says here male gametophyte, uh which is obviously uh in the pollen grain and uh what's going to happen here if I can kind of show this very very nicely as best I can I'll do a larger presentation of this okay so we're going to be looking at the flower and and basically what's taking place so you've imagined we've taken this away this uh is the sticky stigma, this is the style, and basically at the end is the ovary. So pollen grain is going to be transferred obviously by a pollinator and be attracted uh onto the sticky stigma. Now what uh uh happens is a pollen grain is now going to germinate and basically with hydrolytic enzymes is going to digest its way through the style okay? Within the ovary we now have what we're calling the embryo sac, the embryo sack. Folks that is your female gametophyte. Pollen grain is the male gametophyte, right? Remember the function of pollen is to transport sperm nuclei and now two sperm nuclei are going to be produced haploid sperm nuclei I'll just label one sperm nucleus and remember you've got eight haploid cells uh eight haploid nuclei in seven cells, so 1 2 3 4 uh, okay 1 2 3 4 and then you've got 5 6 and there's your central cell with two okay what's going to happen now is this um pollen tube is going to grow uh make its way down and it's going to discharge two sperm nuclei, two sperm nuclei are going to be discharged. One of these folks is uh the egg cell okay, one of the sperm nuclei is going to fuse with an egg cell right there. The other sperm nuclei that has made its way down there's an uh there's an opening in there called the micropyle is now going to go to the central cell and fuse with the two cells in the central cell, okay, here's your central cell. Here's one cell and we won't worry about naming these cells there's another one and here's another sperm nucleus n, n, n, here's the sperm nucleus. This is going to become the embryo. Here's the sperm nucleus, here's the egg nucleus, that's going to become the embryo. The question is what is this going to become? Well look, you've got fertilization it's going to go to the central cell and now you're going to have n plus n plus n fertilization and what's n plus n plus n? It is 3n, that's triploid, that literally is going to become the nutritive tissue that will become the endosperm that will become the starch. So you see in double fertilization we are producing the baby if you will, and we are producing the food supply which is the endosperm uh that's what they're showing in this graphic here where they're showing uh the uh the nuclei and the central cell here, okay, uh fertilization takes place and you wind up obviously with the diploid zygote and now you've got, if I can take that away, you've got the endosperm which is now 3n there's your zygote okay, and there's your endosperm okay, and ultimately you're going to produce uh upon fertilization you're going to produce a seed, that seed's going to germinate and you go back to the sporophyte generation. So this is all very interesting, this is what we refer to as double fertilization uh again if I can show this just for a second feel free to read any of this uh and again after double fertilization the ovule matures into a seed so okay.