A description of the fleshy fruit of Celtis africana (Cannabaceae)

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On 6 April 1999, I encountered a mature specimen of Celtis africana (https://www.inaturalist.org/taxa/133950-Celtis-africana), with fruits at the green stage (https://www.inaturalist.org/observations/67367821), in Newlands Forest in Cape Town.

This is the same location as https://www.inaturalist.org/observations/113935770.

By 27 April, some of the fruits had ripened, and I took the opportunity to describe them in detail.

Celtis africana is indigenous to the Cape Peninsula, where it is the only winter-deciduous tree in the flora.

At the time these notes were taken, the leaves were starting to turn yellow.

I found fruits of all stages of development present together on each branch, suggesting a relatively long fruiting season, at least within this individual.

The fruits were borne in profusion compared to Olea europaea cuspidata (same location: https://www.inaturalist.org/observations/76304954) and Euclea racemosa, both of which were fruiting at this time on the Cape Peninsula.

The fruits of C. africana hardly qualify as bright in hue. However, they do turn from green to yellow. The sweet fruit-pulp is the same hue as the skin.

This yellow is about as vivid as for the fruits of Solanum linnaeanum (https://www.inaturalist.org/observations/39973166), which was still in fruit nearby.

As soon as the yellow hue appears, sweetness can be tasted. At no stage is the fruit sour, astringent, or bitter.

This is certainly a palatable fruit w.r.t. taste and texture. However, it is too small to be profitable for humans, being more suited to birds and e.g. Papio ursinus. Even as a hunter-gatherer, I doubt that I would bother to forage on C. africana (apart from incidental snacking for taste), unless I could collect the fruits by the handful, and then mouth them by the dozen, scraping the fruit-pulp with my teeth, and spitting out the stripped seeds, one after another, before taking the next mouthful.

In other words, I would describe the fruits as 'sweet but meagre'.

The fruit-pulp was somewhat succulent, but firm - unlike the 'watery' fruit-pulp of coexisting O. europaea cuspidata (also in fruit at the time at the same location, allowing direct comparison). The skin is not distinct from the fruit-pulp.

If crushed between thumb and forefinger, the fruit-pulp tends to pop off in a few large fragments. If each of these is squeezed, a bit of free moisture exudes. However, the water content seemed to be at least 10%less than in the case of a distinctly succulent fruit such as O. europaea cuspidata.

The fruits of C. africana would make no stain to speak of, partly because the succulence is not enough for much liquid to ooze.

After the fruits had been processed in my mouth, one or two strips of remnant pulp stayed attached to the circumference-ridgelet on the seed, suggesting the possibility of two-phase dispersal, viz. ornithochory followed by myrmecochory.

The seed seems small and light enough for a large ant to carry, given the handle formed by the circumference ridgelet plus the small remant of fruit-pulp attached to this ridgelet.

'Overripe' stage (https://www.inaturalist.org/observations/22605757):

The fruit soon desiccated to a mealy, instead of succulent, consistency, while still firmly attached by a rather long (about 1.6 cm), thin (but green and apparently alive) pedicel. However, this mealiness was not floury at all, and the fruit-pulp remained sweet.

Both C. africana and O. europaea cuspidata had fruits littering the ground under the crown. However, the ripe and even 'overripe' fruits were not easy to detach, and had to be plucked even when visibly wrinkled, in the case of both C. africana and O. europaea cuspidata.

In both spp., the 'overripe' fruits remained palatable, indeed possibly more rewarding to eat on a weight-for-weight basis than the fully ripe but succulent stage (which has a smooth surface). These qualify, in a sense, as 'natural raisins'.

The fruits of C. africana were on the small side (diameter about 0.7 cm, with a single seed of diam. 0.5 cm), relative to most of the other spp. of fleshy fruits indigenous to the southwestern Cape of South Africa (which generally approximate diam. 1 cm).

There was no pre-ripe display, unless one regards the fully ripe stage as the dull, dehydrated (= 'overripe') one, and the succulent, yellow stage as pre-ripe (which is not logical, because both are equally sweet).

The 'overripe' fruit averages slightly smaller (diam. 0.6 cm), because it is somewhat shrivelled. It is no longer yellow, but instead a dull-ochre hue, i.e. pale yellowish brown (same location: see third photo in https://www.inaturalist.org/observations/114116636). It is both darker and duller-hued than the succulent stage of the ripe fruit.

The yellow stage of the fruit is matt, or at best sub-glossy; the wrinkled stage is certainly matt.

If both stages of ripeness are considered as part of normal range of ripeness, in C. africana, then the overall verdict on the succulence of the fruit-pulp is 'marginally succulent'.

The developing fruit of incomplete size is green. Once it approaches full size, it turns yellow, through a transitory greenish-yellow. There is no delay in turning yellow, once full size is reached.

At both ripe stages, but particularly the wrinkled stage, my mouth could not strip the fruit-pulp off the seed without using my teeth to scrape the seed. Even then, the seed continued to emit sweetness exceeding the maximum sweetness I tasted in the ripe fruits of O. europaea cuspidata. As a result, I found myself keeping the seed in my mouth, as in the case of Grewia and Ziziphus. This could be adaptive in the sense that it would cause mammals to retain the seed in the mouth, thus increasing the distance from the parent plant by the time of spitting.

The seed (4 X 5 mm) is hard, and its surface is more or less spherical with a ridgelet on the circumference, and small-scale pitting. The seed is hard enough to withstand vigorous mouthing by human or baboon, and can be called a 'stone'.

I left a sprig of C. africana lying around indoors for 10 days, then examined it:

• the larger of the green fruits had turned a withered yellow;
• the smallest green fruits stayed green but were now wrinkled; and
• the already yellow fruits had turned brownish, but were still no easier to pluck.

Even after those 10 days, plucking each fruit took a definite pulling pressure, suggesting that the peduncle is designed to stay alive through the 'overripe' stage.

https://www.inaturalist.org/observations/109945662
https://www.inaturalist.org/observations/106061615
https://www.inaturalist.org/observations/67242187

Also see https://www.inaturalist.org/journal/milewski/72570-a-description-of-the-fleshy-fruit-of-cassine-peragua-celastraceae#.

Posted on Νοέμβριος 14, 2022 0816 ΠΜ by milewski