Abstract1. Dissections in the autumn and winter of 1953-54 showed that flower initiation began in seven forms of Rubus at the following approximate times: red raspberry (R. idaeus) var. Lloyd George, early September ; black raspberry (R. occidentalis) var. Cumberland, mid-October; purple-cane hybrid raspberry (R. idaeus x R. occidentalis, a seedling of known origin), early to mid-September; loganberry (East Malling clone), mid- to late September; blackberry var. Himalayan Giant, mid-October ; blackberry var. Ashton Cross, late March ; blackberry (a local wild form), mid-March. These times refer to the primary (main) buds at cane nodes. Initiation generally began later in secondary buds and still later, if at all, in tertiary buds (small buds in the scale-axils of primary and secondary buds).
2. The development of primary inflorescences reached a fairly advanced stage in autumn in the loganberry and in the purple-cane hybrid and red raspberries, but occurred mainly in spring in the black raspberry and in blackberries.