98 ox GROWTH AND CULTIVATION OF WILLOWS IN SCOTLAND. 



stances, may be stated at £25 per acre for Salix mminalis, £30 

 per acre for S. triandra, and £35 per acre for S. purpurea, and 

 when let by contract this is the usual price. 



The current expenses attending cultivation will be as follows, 

 imder ordinary conditions : — 



Weeding per acre, 

 Cutting and tying, 

 Kent and taxes, 

 Interest on outlay, 

 Deterioration, . 

 Incidental expenses, 



The value of willow crops will range from £10 to £20 per 

 acre, according to the state of trade, and the seasons. Occa- 

 sionally they are worth more than twice that amount. But I 

 should not advise any one about to plant, to base their calcu- 

 lations upon extreme profits, lest disappointment ensue. A good 

 return for the outlay may be relied upon in the average of years, 

 and it may safely be said that few if any crops will give better 

 results, provided the rules here laid down are duly observed. 



ON ANIMAL PARASITES. 



By John Scott, 28 Gloucester Street, Regent's Park, London, N.W. 



[Premium — Ten Sovereigns.] 



In the term "parasites" we must include all those animals 

 which derive sustenance in any manner from other living 

 animals — whether by dwelling in or upon the "host," or by 

 merely paying it a passing visit. These are a very numerous 

 class. They do not, however, form a separate or at all distinct 

 division of the animal kingdom, but belong to all its branches, and 

 are found on every class of animals. It will be impossible to do 

 more than briefly notice the most important of them within the 

 limits of a mere essay. 



It is a very common belief that many animal parasites are 

 generated by a diseased condition of the tissues of the host in 

 which they reside ; but a little acquaintance with the life-history 

 of these creatures will prove the error of this opinion, and that 

 the origin of the parasites is to be ascribed to natural, and not to 

 physical causes. 



In a popular classification, the simplest plan will be the best. 

 Without any speculation on a variety of others which present 



