"Nailed fast against a brick wall."
Leeuwenhoek was unable to find any little animals in April. Five weeks later, at the beginning of Letter 31, he wrote to Thomas Gale:
As Mr. Hooke in his letter of April 12th O.S. tells me that you have taken over the foreign correspondence, and will hence-forward answer my letters, this serves to continue my letter of April 5th, in which I noted that I had observed living little animals in the sap dripping from the vine-branches in my court-yard, whereas in the sap that dripped from the shoots of the vine in my garden, I could not discover a living creature.
He spoke of the courtyard behind his house (op mijn plaets) and his garden (in mijn thuijn) as two different places. Later in the letter, he was able to see little animals in the sap. He referred to both the courtyard and garden again, using the same terms.
In the courtyard, the vines were encourged to grow up rather than out.
The tags of leather, with which the branches of the vine were nailed fast against a brick wall, had become wet through.
About 24 hours after I had dispatched my observations to Mr. Hooke the vine-branches in my court-yard dripped no longer and the weather had become uncommonly warm, so that the vine-branches and the leathern tags as well were quite dry. After this it rained nearly the whole night, but in the morning the sun shone and in the afternoon there was once more rain. Seeing that the leathern tags were again wet through I examined the water on these tags (with which the vine-branches, as remarked above, were nailed to the wall) and saw in it several little animals of the biggest sort.