Slatsz' plant photo-biography: Crataegus douglasii, black hawthorn, Douglas’ thorn-apple

10/10/2014 4:09 PM

10/10/2014 7:51 PM

10/12/2014 8:12 AM

Crataegus douglasii, black hawthorn, Douglas’ thorn-apple; Roseaceae family

There are several plants in Drumheller Springs Park, two of them are huge, ordinary size for trees. The others are characteristic shrub size. The huge plants are each in a different ‘thicket’.

There is also an introduced hawthorn, Crataegus monogyna. I hope I haven’t mixed the photos. No problem with the leaves, they are distinctive. The flowers are similar.

The flowering plant in the photo below is the large C. douglasii east of south pond.

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I believe this is the tall stump with ‘suckers’ that supports the blossoming in the photo above.

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So this must be the trunks of the large C. douglasii in tall pine grove.

They don’t look right. I think these are the trunks of C. Monogyna. They slipped into the wrong folder. The burglars are at it again.

No. the leaves are right for C. douglasii. The trunks still don’t look like I remember them. I remember a much larger, even shaggier trunk.

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There may be a dozen plants like these below scattered around the park. The plants in these photos are just west of north pond. I remember more near long rock ridge and near hole in the ground. They will all be on low hillocks, piles of dirt with near bare rock between them. All of the hawthorn shrubs and most of the other shrubs in the park are on hillocks.

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The resources comment that the young twigs are tan, and older bark is gray/black and scarred. And we see that the large trees are very shaggy.

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This is the trunk size I remember in tall pine grove.

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The resources, some of them, put a lot into trying to describe every variation in leaf shape in words and, of course, their language can be impenetrable. There is considerable variation in leaves on the same plant.

The following leaves did not come off the same shrub.

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INFLORESCENCE

Burke: Flowers few in the leaf axils or terminal.

Paul Slichter: The numerous flowers are in flat-topped corymbs.

E-FLORA BC: Inflorescences short, terminal or axillary clusters; flowers several to many, stalked.

Wikipedia: White flowers with greenish centers grow in bunches at the ends of each thin branch.

Jepson Herbarium: Inflorescence: panicle on short-shoot tips, domed;

Missouri Botanical Garden: flat-topped clusters (10-12 flowered corymbs)

Corymb: a flower cluster whose lower stalks are proportionally longer so that the flowers form a flat or slightly convex head. Indeterminate.

Panicle: A loose, branching cluster of flowers, as in oats.

A panicle may have determinate or indeterminate growth.

The character of the inflorescence is easier to see in bud and in fruit than it is in flower. My photos strongly suggest the term corymb is a good label.

Notice in the photos below that the pedicels [the short stems bearing the bud or fruit] are of different lengths but the bud and fruit are about the same level.

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In the photo above, the arrangement of the stems is similar to that of a compound umbel, three stems in this case, rising from the receptacle and branching to support many buds.

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The Wikipedia article on inflorescence says corymbs are indeterminate. If that’s true then a leading bud blossoms and is bypassed as a succeeding leading bud takes its place. The first bud fades and goes to fruit as succeeding buds continue to flower above it or, perhaps in this case, beside it. My photos sometimes suggest the inflorescence has an indeterminate character.

It seems in the photo below that the flowers matured from the center outward, with a few petals clinging to the outermost.

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In the photo below it seems the flowers are maturing from the outside in. However it may be that the mature flowers were the leading bud of each ray rising from the receptacle.

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Sometimes it seems every flower of the inflorescence is in the same stage of development.

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The petals are 5 as with most dicots. The stamen are said to be 10 and the anthers are said to be pink. The number of stamen is said to identify another variety but the numbers compared are 10 and 20 so the observation would be obvious. I don’t see 20 stamen in any of my photographs. The pink character of the anthers does not show up well in my photos.

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Burke says the styles are 5

Paul Slichter says 4 to 5

E-Flora says usually 5 [I see that they say the stamen are 10 to 20]

Jepson says 3 to 5 styles

I don’t have many clear photos of the styles but some show independent styles rising from the ovary.

If you strain a little you might pretend to see some pink in the anthers.

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But several photos show fused styles branching.

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Wikipedia mentions the green flower centers that show in all of these close ups.

In the photo above the fly seems to be feeding on a nectary. The flowers are called fragrant but Missouri Botanical garden says, “Flowers have an unpleasant fragrance which tends to attract pollinators such as midges and butterflies.”

Growing points

Reminder: The ends of stems are growth points and nodes on the stem are growth points.

The inflorescences are both ‘apical’ [at the end of a branch] and ‘axial’. [Axial: In the armpit of a leaf … sorry. It rises above the point from which a leaf arises on a branch [At a node].

More photos to get next year. The photo below seems to show an inflorescence rising from the end of a branch and a single flower rising from the axil of a leaf. However the inflorescence also seems to rise from the axil of a leaf, not really from a receptacle.

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And I don’t have a photo showing a flower rising from a ‘stub’ on a branch. But the resources say it happens.

Here’s a photo of a stub. I think Ken Swedberg told me that these stubs are used repeatedly, that the rings are, in effect growth rings. That’s my interpretation of what I think he said.

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I wonder how the brown structures at the base of the inflorescence below relate to the ‘growth rings’. Perhaps they will fall away leaving scars. Their position suggests that we are looking at an involucre and the brown bracts are phyllaries.

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Crataegus douglasii is of the Roseaceae Family. Roseaceae family plants have an inferior ovary enclosed in an hypanthium.

Reminder:

A superior ovary sits on the receptacle at the top of the stem with the petals and sepals around it. They, too, are attached to the receptacle.

An inferior ovary has the ovary attached to the receptacle but the flower parts are attached to the top of the ovary.

Now I find that I am confused. Is the green stuff growing up, enclosing the ovary [the hypanthium] fused calyx bracts attached to the receptacle or is it the receptacle itself growing up, around and enclosing the ovary with the calyx bracts … the sepals … attached to the top of the receptacle/hypanthium? Or is it something else? I just don’t know.

Something encloses the ovary. The other flower parts are above the ovary.

In the photo above, 300, we might be seeing the receptacle expanding up around the ovary, with pointed calyx bracts [sepals] extending above the receptacle partially wrapped around the petals enfolded in the bud.

In the photos below the petals are opening, the pointed sepals are re-curved. They have pulled away from the petals.

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In the photo below the petals have fallen away but the sepals persist and the withered stamen persist. I think even the withered style persists but its hard to tell in this photo.

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The fruit of Crataegus douglasii is a pome. An apple is a pome. Remember the dry sepals on the end opposite the stem of the apple.

Reminder:

The fundamental female reproductive organ is a carpel. If there is only one it is also called a simple pistil. If there is more than one carpel in the female reproductive organ it is still called the pistil.

The carpels of a pistil with more than one carpel may be fused. If so they are syncarpous. And they may not be fused. If so they are acarpous.

Pomes have more than one carpel and the carpels are fused.

The carpel has three areas, the stigma at the top, the style connecting the stigma and the ovary at the bottom. The ovary encloses the ovum, the egg that when fertilized, becomes a seed. There may be a single ovum. There may be two to many ova.

When the ova are fertilized. The stigma and the style shrivel up. If it’s a dry fruit, the ovary dries and becomes a hard protective covering for the seed. If it’s a fleshy fruit the ovary becomes, guess what, flesh.

The fleshy ovary of the pome is an inferior ovary, it is enclosed in the hypanthium.

In the photos below we watch the green hypanthium turn red, purple and wrinkled up black … they don’t look that black in the photos but they will later, dead black.

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There is a hard coat on the seed. It is poorly exposed in this photo but perhaps you can get the idea. This protective layer for the seed is the inner layer of the ovary.

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