16 



JOUENAL OF THE PLYMOUTH INSTITUTION. 



difference between the value of the produce and the cost of pro- 

 duction. Therefore anything which tends to lessen or increase the 

 value of production tends to lower or raise rents, as the case may 

 be. Thus improvements in agriculture, by rendering land more 

 productive, tend to lower rents; and improvements on land have 

 the same effect. On the other hand an increase of population, by 

 increasing the demand for agricultural produce, raises rents. 



An increase in wealth has no effect on the increase of that class 

 of people who have no position in society which they wish to 

 maintain. The increase of these is only checked by what are 

 called positive checks, such as sickness and hardship. The increase 

 of all others, however, is limited by what is called the preventive 

 check, which keeps them from increasing beyond the means of 

 maintaining their mode of life. Up to this limit, however, they 

 will increase. Therefore, if an increase of wealth is regarded as a 

 good in itself, its benefit will soon disappear before a corresponding 

 increase of needs; and it is only when wealth is regarded by a 

 nation as the means for the attainment of high ends in life that an 

 increase of it can be of any lasting advantage. 



A Paper will be read on the ith November on 



THE FLOEA OF PLYMOUTH: 



ITS DENIZENS, COLONISTS, AND ALIENS. 



By Mb. T. R. Archer Briggs. 

 PROGRAMME. 



Difficulties of Phyto - Geography. — Influence of Man on the 

 Vegetation of the World.— Explanation of the terms Denizens, 

 Colonists, and Aliens. — Purposes for which several Denizens might 

 have been introduced. — Old Popular Kames of Plants. — The 

 Monks as Introducers of Plants.— Popular Names sometimes illus- 

 trative of the History of Species.— Grounds for considering a 

 Species a Denizen examined. — Particulars respecting Trees, appa- 

 rently of the Denizen Class. — Importance of the subject to His- 

 torical Painters.— Critical Remarks on the Origin of some of our 

 Fruit Trees. — Particulars respecting various Herbaceous Denizens, 

 introduced for Food or Domestic Purposes; for Medicine; for 

 Ornament.— Yitality of Seeds. — Colonists.— General Remarks on 

 Plants of this Class.— Ways in which they have been introduced. — 

 Aliens. — The Mistletoe, &c.— Conclusion. 



