The Inheritance of Flowering Time in a Short-Day Species, Solidago Sempervirens L.

BSERVATIONS on the differences in flowering time of various strains of 0 the seaside golden-rod, Solidago sempervirens L., have now been made over a period of several years. This species is a fall-flowering perennial which, in its native habitat, flowers progressively later in the season as one passes from north to south along the Atlantic Coast. When plants from different portions of the range have been grown under cultivation a t the latitude of Rochester, New York, these plants still flower a t different times, those from the north flowering earlier than those from the south. This has been interpreted as evidence for the existence within this species of a graded series of strains genetically distinguishable from one another by their physiological requirements for floral initiation (GOODWIN 1941). A very similar situation has been described by TURESSON (1930) for the European golden-rod, S. virgaurea L., but there altitude is a complicating factor, early-flowering strains being found a t high altitudes even in the southerly portions of the range. A large number of species and strains within species commence to flower in a given locality a t a very definite time in the calendar year, a certain amount of variation being due to minor climatic fluctuations. For example, the regularity with which the three strains of S . sempervirens studied in the present investigation have flowered a t Rochester for the past four years is shown in table I . Through the work of GARNER and ALLARD (1920) and subsequent investigators, it is now known that the principal environmental factor controlling the initiation of floral primordia in many species of plants is the photoperiod. Numerous fall-flowering perennials have been shown to be “short-day” plants,