LATE VARIETIES 347 



cate their taste to beer; they also have antiseptic properties, 

 and are said to prevent the deleterious fermentative action of the 

 lactic acid and other bacteria inimical to the brewer's work, 

 without affecting the action of yeast and the acetic acid bacteria. 

 The third resin, possibly an oxidation product of hop-oil, is 

 pleasantly bitter, with little or no antiseptic power. 



On keeping, the two soft resins lose their useful properties, 

 becoming changed into hard forms. Old ' hops,' therefore, are 

 of inferior value to the brewer. 



The volatile oil present in hops varies from "2 to '8 per cent. : 

 the total resin-content is usually from 13 to 18 per cent. 



Besides the secretion of the glands the bracts and bracteoles of 

 the hop strobile contain within their cells various compounds usually 

 met with in vegetable leaf-tissue. One of the substances present 

 is hop-tannin, which, with its nearly-allied phlobaphene, is no doubt 

 of service in the precipitation of albuminous material from beer 

 wort, although there is much difference of opinion on this point. 



Ex. 171. — Make observations on hop 'sets' and 'cuts' obtained when the 

 plants in a hop-garden are ' dressed ' in spring. 



Note the thick basal portion of the 'bine' which has borne 'hops' last 

 season, and also the number and position of the buds upon it. 



Split one of these ' cuttings ' longitudinally, and note how far the ' bine ' 

 has died back. 



Ex. 176. — Examine which way a hop ' bine ' twines round its support. 



Observe the colour and roughness of the stem, and the shape and position 

 of the leaves upon it. 



Ex. 176. — Examine the structure of a full grown strobile or female inflor- 

 escence of a hop. 



Note (l) the thickness and length of the ' strig ' or axis ; (2) the shape and 

 relative size of the stipular bracts and bracteoles ; and (3) the presence 

 or absence of ripe fruit. 



Which bracteoles are largest, those subtending fertile fruits or those sub- 

 tending abortive fruits. 



Ex. 177. — Carefully slit open a ripe fruit and set free the embryo of the 

 seed ; examine the embryo for radicle and cotyledons. 



Ex. 178.— Examine young strobiles 'in burr.' Make sections of it, or 

 dissect so as to show the female flower and its parts, and the small stipular 

 bracts and bracteoles. 



