Caryophyllaceæ. 253 



E. The Cerastiiim arvense type. 



This type differs from the preceding, by the fact that 

 the prostrate shoots with elongated internodes, have not 

 so short internodes at their base, that they may have there 

 rosettes or rosette-Hke shoot-forms; also they develop 

 roots so abundantly that they might justly be termed 

 "creeping," and vegetative propagation (layering) must 

 be able to take place both by means of aerial runners and 

 — in some species — by subterranean runners. It is a further 

 development of the Cerastiiim alpiniim type. 



To this I refer : Cerastiiim trigy?iiim, С arvense, Moehrin- 

 gia lateriflora, Stellaria longipes, S. borealis and Honckenya 

 peploides. To these may be added of non-Arctic species, for 

 instance Stellaria graminea, S. nemoriim (Warming, 1918, 

 Fig. 14), S. holostea, S. uliginosa and S. glaiica, each with its 

 special peculiarities. 



When, under the Cerastium alpinum type, mention was 

 made of pale, subterranean, plagiotropic shoots, they were 

 probably aerial shoots which had been accidentall}'^ covered 

 over with wind-carried soil and leaves, or had been developed 

 in the shade. Those we are now discussing are, on the other 

 hand, topical subterranean runners with elongated inter- 

 nodes, pale in colour, with scale-leaves and furnished with 

 an apex which can push its way into the soil ; but of course 

 the boundary Hne between these two types is not sharp. 



Cerastium trigynum we will first mention. It has, on the 

 whole, the same mode of branching as С alpinum, but 

 the stems have their internodes, also those at the base, as 

 a rule, elongated. Sylvén mentions, however, rosette-like 

 shoots in the young plants in their first year, and Thekla 

 Resvoll (loc. cit. p. 137, with Fig. 11) records that, in the 

 snow-fields, the internodes of the primary shoot remain short 

 even for a longer period. Branches, at any rate, are developed 



XXXVII 17 



