Walter Oates in 1923, new to his job, clearly knew nothing of Cycads. In his "Short Guide to the Gardens" he mentions two collections of cycads. Of the first, grouped with the palms at the foot of the lawn, he recognises only one species, the widely cultivated Cycas circinalis; the second group, in "Mexico" is without elucidation. He does however make specific mention of: close to the path a fine specimen of the rare Macrozamia Macleayi . Walter Oates 1923
By 1929, he had learnt the names of quite a few. The inference is that these plants existed before his tenure, probably from the early plantings of Francis Cook. Here is his description from the article written for the Gardeners' Chronicle: Cycads are represented by fine plants of Dioon edule, Encephalartos Lehmannii, E. villosum, E. horridus, Cycas revoluta, C. circinalis, Macrozamia spiralis and many other species. On the lawn, standing alone, is a magnificent plant of Macrozamia Macleayi, with a trunk 3 ft. high, 2 ft. thick, and with three large branches, each bearing broad, pinnate, glossy, dark-green leaves 6 ft. to 8 ft. long. Walter Oates, 1929
Already in 1885 Macrozamia miquelii was grown (as Macrozamia mackenzii)
Encephalartos: lehmanii, villosum, horridus
Cycas: revoluta, circinalis
Macrozamia: spiralis, macleayi, miquelii
To this list Javier Segura adds Ceratozamia mexicana from recent observation. The Encephalartos and Macrozamias have disappeared.