1923] Bau: Morphological Characters in Crepis Capillaris 221 



With regard to the method of cross-pollinating the plants, both 

 the methods suggested by Babcock and Collins (1920) were tried, 

 and depollination with a water jet has given results as good as emascu- 

 lation, although the latter method was employed in all cases of critical 

 investigation. The flowers were enclosed in translucent paper bags 

 to prevent insect pollination and the achenes gathered before they 

 were over-ripe and dropped to the ground or were taken off by the 

 wind. It is fairly easy to decide whether a cross-pollination has been 

 successful or not because the involucre assumes an ovoid form in the 

 successful crosses, whereas it remains more or less oblong in the unsuc- 

 cessful ones. The achenes, moreover, are plump and the ribs marked, 

 the seed coat itself being distinctly colored as compared with that of 

 the unfertilized achenes. 



INHERITANCE OF LENGTH OF LEAF 



In Crepis capillaris the first true leaves are small (about twice the 

 size of the cotyledons), and there is a continuous increase in leaf size 

 until the rosette is formed. Plate 42 shows stages of growth of the 

 leaves including the mature rosette when they are ready for measur- 

 ing. Even in the early stages the plants show different habits of 

 growth, some growing erect and others spreading horizontally. In 

 one family especially (20.6) there is a tendency for the leaf margins 

 to curl downward, thus rendering measurement difficult (plate 42, 

 fig. 4). In the earlier work, the leaves were clipped off with a pair of 

 fine scissors close to the stem and measured on a centimeter ruler. 

 But later on it was thought that injuring the plants thus might affect 

 the result, and the leaves were kept intact on the plant while the ruler 

 was thrust in as close to the stem as possible. Five mature leaves 

 were measured at random and the average of the readings has been 

 taken to represent the mean length of leaf in the plant. In table 1 it 

 will be seen that the length of leaf fluctuates widely from the mean 

 as compared with the breadth. The variation in length was 12.6 to 

 23.0 cm. in family 20.1, 11.8 to 18.4 cm. in family 20.6, 15.8 to 30.7 cm. 

 in family 20.11 and from 24.0 to 40.1 cm. in family 20.13. Crosses 

 were made between the 20.1 family with a range from 13 to 23 cm., 

 and family 20.13 with a spread of 21.0 to 40.1 cm. with a view to 

 studying the way in which the factors for length segregated. Table 

 2 gives the usual biometrical data for the various families studied. 

 This table indicates that the factors for length show segregation in F., 

 but owing to the fact that the environment plays such a great part in 



