The arrangement of Sepals and Petals in Parnassia palustris L.

The aestivation of the calyx and corolla in 640 flower budsof Parnassia palustris L. from two sites in Britain is recorded. Only two types of calyx arrangement are found. They are quincuncial,one being the mirror-image of the other and they continue thespiral from the bracteoles in the left or right direction respectively.The two types occur in almost equal numbers. Twenty-two of the possible thirty-two corolla arrangements arefound and there is a predominance of apotactous forms. The convolutecorolla does not occur. The three commonest corolla types foundin flowers with a right calyx are respectively the mirror-imagesof the three commonest corolla types in flowers with a leftcalyx. Corolla arrangements differing greatly from the six commontypes are rare. Although the completely eutopic corollas arenot found, the commonest types are strongly eutopic and thereis a highly significant tendency to eutopy in each sample asa whole. In flowers of each calyx type the overlaps betweenthe two posterior petals and on the ß-bracteole sideof the flower are predominantly eutopic whereas the two overlapson the -bracteole side involving petal 9 are nearly always metatopic. These observations are compared with those made on other specieswith variably imbricate pentamerous corollas and their significanceis briefly discussed.     

The Morphology of the Inflorescence in Ranunculus bulbosus L.

This paper records the form variation of 750 inflorescencesof Ranunculus bulbosus L. collected randomly from each of twolarge colonies growing on permanent grassland. Each inflorescence has a terminal flower, 1–4 bracts onthe main axis and up to 8 flowers borne on cymes subtended bythese bracts. Over 75 per cent, of each sample consists of inflorecenceswith 2 or 3 bracts on the main axis and 2–4 flowers. Thenumber of flowers increases with the number of bracts on themain axis and evidence is given that the 4-bract 9-floweredinflorescence may be nearly the largest and most complex thatcan be produced under these conditions. The distribution of flowers in the axillary cymes is such thatthe inflorescences tend to be radially symmetrical and pyramidalin form. This is so even thought with increase in the numberof bracts on the main axis the proportion of axillary flowersdecreases in the lowest cyme and increases in the cyme above. It is considered that the form and size of the inflorescencecan be related to the vigour of the plant and to the mechanicaland nutritional problems involved. A comparison of the varioustypes of inflorescences found probably reflects the developmentalsequence of flower production. It also indicates that thereis competition between certain potential flower positions asthe inflorescence develops.