T.vxoxo^^c studies ix the gexus cerastium 



By F. H. Whitehead 



UniveTsity of Oxford 



This species \^.-as f_rst described from Scandiiia\ian material and is ger-erady regarded 

 as lia\iiig a predciT-ir-anily S. Swedish distribution. It has, hov\-e\-er, been reported from 

 time to time as occurring in the British Isles. An examination oi material in the Druce 

 Herbarium, Oxford University, showed that the determination of specimens labelled \j.dth 

 this name was doubtful. For example, one sheet has specimens which Druce sent to 

 !Murbeck for verification and which he returned with his opinion that they belonged to 

 C. atrovirens Bab. Nevertheless, these ".-ere labelled as C. subtetrandrum by Druce and 

 included in his herbariimi imder this name. Dcubt has also been thro\^-n in the past on the 

 correctness of the determination of material included under his name in other herbaria. A 

 close examination of material collected in Sweden and determined by \furbeck, who first 

 described the species, showed that there exist a number of differences bet^'een it and British 

 material determined as C. suhtetrandrum. The seed size of the Swedish material appeared 

 to be smaller whilst the pollen size u-as larger. The petals also were much broader in 

 relation to their length in the Swedish material. Other characters, said to be of diagnostic 

 value, were also examined but were found not tc be czrrelated. These latter characters 

 were seed colour, the ratio sepal-length petal-length and plant colour. The seeds of 

 C. suhtetrandrum are said to be Hght in colour whilst those of C, atrovirens are dark broun 

 CMurbeck, 1898). Fresh Swedish material of C. suhtetrandrum vrzs examined and found 

 to have pale yeUow-brown seeds; herbarium material, often of some age, of plants from 

 similar habitats usually W3s fotmd to have similar coloured seeds. Some specimens, how- 

 ever, had seeds :: a much darker colour, but it was noticed that these specimens had 

 become damp and that decay had set in at some time subsequent to their collection. The 

 darker colour these seeds may be due to this decay. The colour of freshly gathered 

 C. atrovirens seeds is usually dark reddish broum but some plants have paler seeds. These 

 latter plants are usually from the north of the British Isles. 



The sepals of the Swedish material were foimd to be much longer than the petals 

 and usually more pointed than the sepals of most plants of C. atrovirens. However, some 

 plants of C. atrovirens were also found to have sepals much larger than the petals and this 

 character was found to be scattered throughout the British C. atrovirens pop^ulation. 



A personal communication from Bengt Pettersson stated that C. suhtetrandum is always 

 a paler and more yellow green than C. atrovirens. Plants were grown from seed taken 

 from plants determined by him and also checked by the discriminant analysis which 

 follows. These plants weie found to var>- in colour and growth form in relation to hght 

 intensit\- as did other Cerastia (Whitehead, 1956) - the higher the light intensitv- the 

 more anthoc\-anin, etc. Since C. suhtetrandrum is usually foimd growing amongst grasses 

 on the edges of dunes rather than in the exposed situations more common for C. atrovirens 

 this may account for the obser\-ation that C. suhtetrandrum is usually of a paler and more 

 yellow shade of green. 



A discriminant analysis, as described in the pre\ious paper (Whitehead, 1955), has 



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