190 Sterile " Dvarf^" in Hiinmlus LupuUis L. 



of cocoa-nut string (such as is used in hop-gardens for " training" hops) 

 and "trained" round it from time to time through the summer, will 

 climb in rather a feeble manner and reach a height of 3 to 5 feet. No 

 better climbing habit is shown if the shoots are allowed to gi-ow up 

 finely-branched pea-sticks. In the majority of cases a "dwarf" pro- 

 duces a large number of thin shoots, which radiating from the rhizome 

 run prostrate on the ground and produce a " mat "-like growth covering 

 a square yard or more (see PI. VIII, fig. 1); in rarer cases a few of the 

 shoots if carefully " trained " raise themselves by climbing round each 

 other and the cocoa-nut string, either to a height of 5 feet, as shown 

 in PL VIII, fig. 2, or more usually to a height not exceeding 2 feet 

 (PI. IX, fig. 3). The leaves on the "dwarf" are much smaller than 

 those on the normal hop-plant, and are less divided, being often unlobed, 

 and never more than 3-lobed ; the diameter of the stem at its base does 

 not exceed ^ in., and is often less than ^ in., whereas in the normal 

 plant it is from | in. to ^ in. The stem of the " dwarf" possesses the 

 hooked hairs found in the normal plant. So far as has been observed, 

 the root-system of the 'dwarfs" is characterised by none of the roots 

 running horizontally; further, no underground stems gi-owing hori- 

 zontally (" runners ") have been seen in the dwarfs. 



The distinctive characteii sties of the "dwarf" are usually evident 

 soon after germination. A normal seedling produces in a few weeks 

 a stem with a strongly developed climbing habit, which, in the case of 

 a vigorous plant, will reach at the end of the first year's growth, to a 

 height of .5, or even 6, feet. In cases where " dwarfness " is most 

 marked, the seedling plant produces in its first year one or more shoots 

 of very limited growth, which never climb and which bear abnormally 

 small and often curled leaves ; at the end of the season's growth the 

 whole plant may be only 1 inch high. In other cases, where the 

 " dwarfness " is not so extreme, a number of shoots are produced, which 

 may reach to a length of 6 to 9 inches ; none of the stems, however, are 

 able to climb. In the second year from germination, the normal seedling, 

 whether male or female, produces a fairly stout stem, which climbs to 

 10 feet or more, and produces flowers. A normal seedling developing 

 the fresh shoots in the spring of its second year is shown in PI. IX, fig. 4. 

 In the case of " dwarfs," the one-year-plant if vigorous produces the next 

 spring a number of shoots, with thin .sometimes almost thread-like 

 stems, which never climb, but run prostrate over the gi'ound and attain 

 a length of 2 to 3 feet. No flowers are ever produced (as noted below). 

 PI. IX, fig. 5 shows a one-year-old " dwarf" .seedling, starting the season's 



