MUTATIONS, VARIATIONS, AND RELATIONSHIPS OF THE OENOTHERAS. 29 



of these studies. The oenotheraceous bud offers distinctive characters for 

 the separation of the several species (plate 8). It has, as is well known, three 

 distinct regions, the ovary, the hypanthium, and the cone — which are in most 

 cases marked off from each other in such a way as to make their accurate 

 measurement easy. As proof of this fact it is only necessary to say that fre- 

 quent repetitions 

 of the measure- 

 ments showed only 

 a variation of one- 

 tenth of a milli- 

 meter in the thick- 

 ness of ovary and 

 hypanthium, and 

 from 0.2 to 0.3 mm. 

 in thickness of the 

 cone and lengths of 

 the several regions, 

 the maximum error 

 in the smallest 

 measurements 

 taken being less 

 than 4 per cent of 

 the magnitude 

 measured, and in 

 the larger measure- 

 ments, such as 

 length of hypanthi- 

 um and cone, less 

 than I per cent. 



In deciding to 

 make statistical 

 studies on buds a 

 careful preliminary 

 survey was made 

 to determine what 

 precautions would 

 need to be taken 



in order to free the work from error. The several points that seemed to need 

 consideration were: (a) A probable periodicity in the size of the buds, so that 

 those in the earlv part of the season are doubtless a little larger than those 

 produccdnear the end of the season, but as the flowering season isverylong this 

 periodicity is certainly slight and would probably have noappreciable influence 



Fig 



8. — Corrclalii 111 betwcc-n width (subject land Icngtliof k-af in Oi iiothciti 

 I iibi iucriis. Measurements in millimeters. Coefficient of correlation, 

 4452±0.0171. 



