With the upright position of the reeds, the stopper of the opening would receive the rain and would become diluted; the ceilings of the storeys would fall in and the family would perish by drowning.
Therefore the Osmia, who knew of these drawbacks before I did, refuses the reeds when they are placed perpendicularly.
The same reed is used for a second purpose.

We make canisses of it, that is to say, hurdles, which, in spring, serve for the rearing of Silkworms and, in autumn, for the drying of figs.

At the end of April and during May, which is the time when the Osmiae work, the canisses are indoors, in the Silkworm nurseries, where the Bee cannot take possession of them; in autumn, they are outside, exposing their layers of figs and peeled peaches to the sun; but by that time the Osmiae have long disappeared.

If, however, during the spring, an old, disused hurdle is left out of doors, in a horizontal position, the Three-horned Osmia often takes possession of it and makes use of the two ends, where the reeds lie truncated and open.
There are other quarters that suit the Three-horned Osmia, who is not particular, it seems to me, and will make shift with any hiding-place, so long as it have the requisite conditions of diameter, solidity, sanitation and kindly darkness.

The most original dwellings that I know her to occupy are disused Snail-shells, especially the house of the Common Snail (Helix aspersa).