Saturday, May 26, 2012

Field Sketches

Arum italicum

Arum Study, pencil & color

Last Saturday in our botanical art class we continued learning about how to identify plants, their parts, and how to create field studies of them. In the afternoon, (it was a gorgeous day), we went out on the classroom grounds at McCrillis Gardens to practice. The idea was to do a quick gesture sketch of the entire plant to give an idea of its habit, then fill some of the details, making notes on color. Next, look closely at the flower and analyze it, drawing it so that all its parts can be seen clearly.

I selected this arum species because their curious flowering structure, called a spathe, caught my eye. They were all over the understory, edging other plantings.

Last fall when we were studying leaves in Drawing 102, the vein patterns of the leaves and their curling edges appealed to me, and I did several  sketches of these, so the leaves were already familiar, but I had no idea about the particular species of arum. I later searched on-line and found it is called Italian Arum.

To examine the flower, I found another specimen that was a bit more developed than the first one photographed above, and cut apart the papery hood to reveal the curious details inside. The female flowers at the bottom of the shaft appeared to have been fertilized and were developing into seeds. It seemed likely that the middle bump of small grains were the male flowers, but what about the ring with long hairs above it? That was a bit of a mystery, so later I went on-line to research.

According to Wikipedia, the upper ring of hairs functions as a trap for insects. The pollinators are beetles or other crawling insects which are attracted to the spadix (the club-shaped organ) by its odor of decay and temperature several degrees warmer than the ambient. The insects get dusted with pollen and when they escape they take the pollen to another spadix, ensuring cross-pollination. The purplish color at the bottom of the spathe has the tinge of carrion, another good indicator about the kind of insect pollinators.

At the bottom left of my sketch is the further developed fruit of the Arum, again found on another specimen nearby. Here the spadix has almost rotted away as the stem grows into a pineapple-like fruit. The seeds will turn red when ripe, much like the seeds of Jack-in-the-pulpit.

We were instructed to collect parts of the flower and seeds and preserve them by sealing them under transparent packing tape. We are to include these with our finished drawing. In my case these specimens were so bulky that I was only able to put them under tape by pasting them onto a piece of paper. Unfortunately, this did not seal them completely and my specimens have already lost their color. I had included some color notes with color pencils on my sketch. That may have to do unless I can collect some new specimens and seal them better. I may yet go back to McCrillis to do just that.

It's all so fascinating!

Sunday, May 6, 2012

The Secret Sex Life of Ladyslippers

Yellow Ladyslipper in Virginia Forest

Yesterday my friend Linda and I went out to hike at the Thompson Wildlife Management Area in Virginia. This is one of the richest places in our area for spring wildflowers, and one particular portion, with its spectacular display of Trillium grandiflora that extends for acres, is known as the Trillium Trail (previous postings about it here and  here ).

We hadn't visited the Trillium Trail for a couple of years, and with this year's unusually warm spring putting our season two weeks ahead of a normal year, I was fairly sure the trillium display would be over by now.

We found some fading trillium flowers in small patches here and there (the white flowers turn pink as they age), but the main reason I wanted to make the trek was to find some yellow ladyslipper orchids for my botanical studies. The yellow ladyslipper seems to be prospering at this site, and my impression is that each year I've visited there are more flowers to be found.

I'd brought my sketchbook and pocket magnifier to make some field sketches of the flower's reproductive parts, but what exactly these were in this species, and in orchids in general, I wasn't really sure. I hoped direct observation would help clear up the mystery.

All flowers need pollinators to set seed, and orchids have evolved some of the most unusual strategies to accomplish this. Some orchids mimic bees or moths to attract specific pollinators, but in the case of the ladyslipper, the pouch forms a trap for the insect. The flowers produce nectar to attract the insect, presumably some kind of bee small enough to fit through the opening. In order to get out, the insect must crawl up towards that small protuberance you see in the photo, called the staminoide. Under the staminoide you can barely see two tiny pollen sacs, the anthers, which will drop their pollen on the insect to transfer it onto the stigma.

 I was lucky to find some decaying flowers where these parts were clearly visible. I was also fascinated to learn from my on-line research that the seeds have a very tough outer covering and need the help of mycorrhizal fungi to germinate and get nourishment during the early part of their life cycle. No wonder they are flourishing here--there is plenty of fungi all over this forest.

The young corm may not develop a true leaf for several years, but as it develops into a rhizome and produces more leaves, eventually it will no longer depend on the fungi. A plant may take up to sixteen years to produce its first flower, but they are long-lived plants.

I'll want to come back in mid-summer to see what the seed pods look like, and how many of the flowers have set seed. The secret sex life of these lovely orchids is fascinating!