The years are conjectured from the form of the address printed on the stationery and by the reference to returning a book ‘to-night by our Carrier’. CD used this form of printed address between 1861 and 1869 (Carroll ed. 1976, p. xiii). The Down parcel carrier, George Snow, departed for London every Wednesday night; between 1861 and 1869, the only Wednesdays that fell on 8 January were in 1862 and 1868.

The reference is probably to one of the botanical works of the Greek philosopher Theophrastus, who is mentioned in Variation 2: 308 in a citation from A. de Candolle 1855.

The reference may be to Ernst Friedrich August Boll; the work has not been identified.