184 Variatioii In t/ic Male IInji, lluimilus hipulus L. 



\ inch in fliametcr was punchod throu<;h a piece of thin sheet metal 

 about 2 inches square; this metal plate was so placed on the leaf 

 under examination that the circle came midway between the sinus 

 at the base of the terminal lobe and the junction of the petiole and 

 lamina. By means of a pocket-lens majjnifying 10 diameters, the 

 glands as a rule can easily be counted ; when the glands are numerous 

 the smaller veins are often of service, since they di\'ide the circle into 

 smaller areas which can be taken in order. In this way two countings 

 could be made for any one leaf, one on each side of the mid-rib. Two 

 leaves were selected from eacli hill, one at the level of the breast-wire 

 and the other midway between that wire and the top wire; thus four 

 readings were taken for each hill each year. In each of eleven cases 

 36 countings have been possible, i.e. where three hills have the same 

 origin, and the general conclusions arrived at are based chiefly on the 

 average obtained from 3G such countings in each case, although in 

 certain typical examples fewer readings were taken, since two hilLs (or 

 perhaps only one) of each were available. 



Although there is often considerable variation in the number of 

 glands borne by the leaves of a single plant, this variation (for a \ in. 

 circle as indicated above) is about a certain mean which may be as high 

 as 80 or as low as 20. Usually the number lies between 40 and 60; 

 thus in the eleven $ hops from each of which 3G countings were possible 

 the following numbers were obtained : 



No. of glands to } in. circle 



Reference numbers 

 of hills 



Lower leaves 



Mill. 



Max. 



Av. of 18 



pountinss 



Upper leaves 



Mill. Max. 



.\v. of 3fi 

 t'(iuntin£r.s 



Av. of 18 



count inss 



A 13 [-315; 

 B 1 1 [ - 2!IS ; 

 C7 [=300; 

 U 22 [=32-1; 

 F2 [=3(m; 

 K 10 I -311: 

 E l(i| ^ 44; 

 t!27[-3l!): 

 Z 12 I =2il2: 

 .30 [= 35; 

 108 [ = lfi7; 



106 

 87 

 88 

 70 

 51 

 70 

 74 

 78 

 r>4 

 102 

 \-A 



75 

 55 

 59 

 51 

 34 

 44 

 46 

 46 

 41 

 50 

 00 



42 

 33 

 33 

 32 

 21 

 25 

 25 

 26 

 25 

 34 

 50 



04 

 «7 

 65 

 78 

 36 

 58 

 49 

 65 

 52 

 64 

 101 



M 



rA 



47 

 47 

 28 

 37 

 35 

 39 

 44 

 47 

 74 



69 

 53 

 53 

 49 

 31 

 11 

 41 

 43 

 42 

 53 

 82 



A comparison of the above figures shows two features of interest: 



