3GG 



INTRODUCED PLANTS IN WEST CORNWALL. 

 By W. Roberts. 



The plants in the following list nearly all occur, or have 

 occurred, within a few yards of one another on a barren piece of 

 ground known as the Eastern Green, which borders the railway- 

 cutting between Penzance and Marazion, and fringes the beach. 

 Within a mile, in a direct line inland, is situated an extensive flour 

 mill, which receives large cargoes of wheat from ports in America, 

 from Dantzic, from the Black Sea and the Sea of Azov, and from 

 Egypt and India. As the corn is winnowed on the Eastern Green, 

 and as in the nature of things it inevitably contains a greater or 

 lesser percentage of the seeds of various weeds, it is only natural 

 that some of this "chaff" falls on suitable soil and springs into 

 growth. 



In most cases their life is brief, and in very few instances do 

 they appear a second year. They rarely give one the impression 

 of being typical specimens. The climate in the first place, the 

 station in the second, and the fact that the ground is already 

 densely occupied with vegetable growth of a vigorous character in 

 the third, are fatal elements to the acclimatisation of weakly corn- 

 field denizens. The plants in question appear, for the most part, 

 to thrive only under special circumstances, although the geo- 

 graphical distribution of nearly every one is wide. DeCandolle, in 

 his ' Geographie Botanique Raisonnee,' tells us that it is not so 

 much a total annual average amount of heat that a plant requires 

 to enable it to vegetate, to flower, or to ripen its seed, as that this 

 heat shall never descend below or ascend above certain extremes, 

 and that it shall remain within those limits for a sufficient length 

 of time for the completion of these operations, a period of time 

 which may be shortened or lengthened according to the greater or 

 less intensity of the heat received by the plant within the above 

 limits. This exactly defines the position of the colony of additions 

 to the Flora of West Cornwall. The absence of extremes — heat 

 and cold — is fatal to their welfare. It is also an interesting fact to 

 note that nearly the whole of these additions are normally of 

 annual duration, so that the chances are materially increased 

 against self-propagation. 



I am indebted to a local botanist, Mr. W. A. Glasson, for a 

 complete list, and also for specimens : the names have been verified 

 by Mr. N. E. Brown. The "Eastern Green" and the neighbour- 

 hood which terminates at one point with the Marazion marshes is 

 peculiarly rich in its flora, and during the past half-century the 

 late John Ralfs noticed and recorded the names of several plants 

 to which, regarding as aliens, he paid very little attention. Mr. 

 Glasson began his observations in the summer of 1885, when he 

 found Saponaria Yaccaria, which had been observed near the Logan 

 Rock in 1878 by Dr. Fraser ; the next species, which had also been 

 observed before, was Echinospermum Lappula, and, finding these two 

 plants, Mr. Glasson was led to pay close attention to the district. 



