Sorting and blending of unit characters. 197 



characters" thus far analj^zed. By this means the striking differences 

 of the two parents will be seen and we shall be in a position to 

 appreciate the distribution, or blending*, as the case may be, of the 

 characters in the different hybrid types. The parents differ by more 

 than thirty easily recognizable contrast pairs of "unit characters", or 

 allelomorphic pairs, or, if we speak of them in terms of the "presence 

 and absence" h3^pothesis, there are more than sixty factors of recogni- 

 zable characters which meet in the fertilized egg of the cross between 

 the two parents. These characters relate to the habit and coloration 

 of the adults; features of the rosettes, foliage and inflorescence. The 

 habit and morphological characters are well shown in the photographs here 

 reproduced (Fig. 1). The measurements given are for the garden cultures. 



Oe. pycnocarpa. Habit; tall, 1 — 1*5 m; lower stem branches 

 numerous, strict, not widely spreading, reaching about the middle of 

 the main stem, main stem therefore with liigh overtop, tips nearly the 

 same level; axillary rosettes over the middle and upper part of themain 

 stem, or short flowering branches just below the main inflorescence. 

 Autumnal rosettes compact, the larger leaves (late summer and early 

 autumn leaves) narrow, cut over the basal half, furrowed, repand, white 

 veined, plain or only slightly buckled, no reddish spots. Stems green, 

 tubercles green. Stem leaves, narrow, white veined, slightly sinuate 

 toothed (lower ones strongly so over basal portion), furrowed, plain, no 

 red spots. Inflorescence long and dense; bracts green, slightly sinuate 

 toothed, longer than the flower buds, persistent, basal ones longer than 

 the pods. Petals lemon yellow, cuneate, strongly emarginate, not 

 plicate, edge plain, medium size, firm, not quickly wilting. Fertility 

 high (pods with many viable seeds). Plant flowering for a long period 

 and maturing late. 



Oe. nutans. Habit; medium height, ^U — 1 m; lower stem bran- 

 ches numerous, spreading irregularly, reaching far above the middle of 

 the main stem, main stem therefore with low overtop, tips at unequal 

 heights not terminating at the same level; axillary rosettes over the 

 middle portion of the stem; short flowering branches at base of the 

 main inflorescence. Autumnal rosettes compact, the larger leaves 

 broad, sinuate toothed over the basal portion, convex, not repand, red 

 veined, strongly crinkled, reddish spots in the autumn. Stems dark 

 red sometimes also the base of inflorescence axis is red, otherwise the 

 inflorescence axes are green; tubercles red, even over the green parts 

 of the stem, rarely red on the young pods. Stem leaves broad, very 



