This entry was schedule to appear yesterday. Unfortunately an unknown problem arose and it did not appear as scheduled. My apologies.
Today's entry was written by Randal Mindell, a botanist working on a special project at UBCBG. Randal took the close-up photo and I took the full view. Randal writes:
Fronds of Osmundastrum cinnamomeum (cinnamon fern) come in two forms: tripinnate vegetative fronds and tripinnate reproductive fronds. This differs from the coupling of reproductive structures on vegetative, photosynthetic leaves common to the vast majority of filicalean ferns. The distinction between the two frond types is easy to see in the picture, with tan fertile material encircled by traditional, verdant foliage. If you feel like you have seen this before, perhaps you are thinking of other erect and iconic ferns such as Blechnum spicant (deer fern), Onoclea sensibilis (sensitive fern) or Matteuccia struthiopteris (ostrich fern).
Among living ferns, the family Osmundaceae has one of the longest fossil records. It traces back to the Paleozoic, and is widely distributed across the northern hemisphere during the Mesozoic. Given the widespread nature of Osmunda cinnamomea in the present (North & South America, Asia), I would like to reflect on the reproductive potential that fuels its dispersal. Plants here at the garden give off anywhere from 5-10 fertile fronds. An informal count revealed that these fronds produce anywhere between 11-19 pairs of primary pinnae (primary divisions of the leaf), which in turn give off anywhere between 13-20 pairs of secondary pinnae. Counting the tertiary pinnae (the sterile tissue on to which the sporangia are borne) is too painful, but a count of sporangia on a few secondary pinnae averaged 45 per pinna. Putting these loose numbers together (fertile fronds × primary pinnae × secondary pinnae × sporangia per secondary pinna) and multiplying them by the 64 spores per sporangium that is standard for the Dryopteridaceae, we see that one individual has the potential to produce anywhere from 8-43 million photosynthetic spores.
The sterile fronds do resemble ostrich fern; however, the fertile fronds are really reminiscent of cinnamon fern. Ostrich fern fertile fronds appear more structured, even when immature.
Back in the 1930s, my mother surrounded our cottage on three sides with beds of such ferns. Heaven help us if we shook blankets, or even thought about climbing over the railings. They were her pride and joy - huge lush things that looked wonderful and hid the bottom part of the cedar cottage walls.
Some friends rode their bicycles out from Toronto one summer, and mother thought she would learn to ride one. She got so she could do pretty well on the flat, and one day decided to go round the cottage - down a slope, across the flat and up a steeper slope. 'Twas the latter that got her - over she went into her lovely fern bed, squashing them flat. We tried fairly hard not to laugh, but never let her forget what she did to her own ferns.
I hate to quibble with a botanist but I must agree with Robert that these fertile fronds look much more like cinnamon fern than ostrich. I have both growing near my house here in Maine; cinnamon fern is "blooming" now, but ostrich fern's fertile fronds will not appear until later in the summer.
I think the photo is one of Cinnamon fern also. Oops!
Great pictures showing both the form of the whole cluster and a close-up of the fertile and leafy fronds. However, I question the identification and am inclined to agree with Robert above that this is a photo of Osmunda cinnamomea (cinnamon fern).
While Matteuccia struthiopteris (ostrich fern)is also a large, handsome fern whose fronds grow in a cluster and also has separate fertile and sterile fronds,the two have some different characteristics. The fertile frond pictured has the classic cinnamon color of Osmunda cinnamomea. It disperses its spores shortly after it reaches its full height,early in the season, and then withers away. The fertile frond of M. struthiopteris appears more mid-season and is first a very dark green and ages to a dark brown-black. The stiff structural part remains through the winter and disperses its spores before new leaves emerge in the following spring.
The leafy fronds of both ferns are similarly bipinnate. However the pinna of M. struthopteris are longest toward the top, perhaps 1/4 way down the rachis, and at the bottom are very tiny. The sterile fronds of O. cinnamomea, however, are widest in the bottom half, and the lowest pinna are smallish but not tiny. Only O. cinnamomea has wooly tufts on the back where the pinna join the rachis.
Both ferns enjoy damp to wet soils. They are easily confused. At least that's the way it is in New England.
I don't understand the phrase "photosynthetic spores."
Are the spores photosynthetic while the are growing on the fertile frond?
Our readers are correct. We goofed. The entry has been corrected, but was originally titled Matteuccia struthiopteris.
Hi,
I think Randal may have significantly underestimated the spore output of his plants. Most ferns produce 64 spores per sporangium, but ferns in the Osmundaceae produce more:
128 in Leptopteris and 256 or 512 in Todea and Osmunda / Osmundastrum.
Ciao
Brian
Gorgeous photos, both, and interesting discussion. I always learn from you, and always enjoy the beauty. Thanks!
Exelente macro ... Felicidades ...