It is probably no surprise that something with the epithet plumosa has the word “feather” in the common name. Feather cactus is native to the states of Coahuila and Nuevo Leon in northeastern Mexico.
The feathery bits are radial spines. Up to 40 of these are attached to each areole. As some readers may remember from earlier entries, cacti spines are modified leaves. Areoles are similarly highly-modified structures, analogous to branch buds.
Mammillaria plumosa grows into a low, dense mound, perhaps reaching 40cm (16 in.) in width. Its preferred habitat is calcareous rock clefts–I would guess fully-exposed to the sun because of the (likely) adaptive properties of the feathery spines. Presumably, these have a 3- or 4-fold effect of: reflecting light (the whitish colour); radiating heat (expanded surface area), shading the surface of the plant (so that biochemical reactions can operate at more optimal temperatures), and possibly preventing water loss (through reducing the evaporative effects of moving dry air). The flowers are also white, and these can be seen linked from the Wikipedia page: Mammillaria plumosa, or via the University of Connecticutt’s Biodiversity Education & Research Greenhouses: Mammillaria plumosa.
Lastly, a roundup of some University of British Columbia news that may be of interest:
- Are you the world’s next top PhD student? UBC’s Faculty of Forestry is seeking a high-calibre individual for its Future Forests Fellowship. If not the world’s largest forestry scholarship, it is certainly up there: up to $280 000 ($70 000 annually for up to 4 years) to support a student in one of the fields of Forest Products Biotechnology / Bioenergy / Forest Genomics / Climate Change / Urban Forestry / Forest Management / Conservation / Forested Landscapes / Salmon Ecology / Forest Health / Forests and Indigenous Peoples / Forests and Human Health.
- UBC’s (relatively) new President, Santa Ono, has recognized UBC’s strength in biodiversity research by establishing a President’s Excellence Chair in Biodiversity Studies, one of only six such chairs
- UBC’s Beaty Biodiversity Museum has a weblog entry about the recent provincial fires threatening an important collection: Precious Lichen Collection Evacuated from BC Wildfire Zone
- I’m happy to report that we’ve secured funding within the UBC Work-Learn program for a student to assist with BPotD starting in the autumn, so we’ll have another fresh voice soon. The backlog of entries that previous students had authored is dwindling!