THE STUDY OF THE EVOLUTIOK OF THE FLO WEE. 



extremely rudimentary in Sambucus, and obsolete in the uniovulate loculi of Symphori' 

 carpus. The parietal region is also small in Aralia and the Hamamelidacese. 



2. Progressive abortion in the ovary is associated with progressive sterilization. 

 Physiologica,l sterility occurs mLonicera where although the lonuli are pluriovulate, only a 

 few^ seeds are formed in the ovary. The sterility of particular ovules is notpre-.determiced. 

 In Symphoricarpus the ovules of the pluriovulate loculi, which are similar in form to the 

 fertile ovules, are definitely sterile. The megaspores are not arranged in a linear row, 

 as in the fertile ovule, and the embryo-sacs are incomplete. In Viburnum tiie sterile 

 ovules are very imperfect. The integument and raphe are considerably reduced, and the 

 sporogenous tissue develops abnormally. The ovules in Samlucus are represented only 

 by a few cells. The Hamamelidacese also show stages in reduction in the number of 

 ovules, but the stages are not similar in the two families. 



3. The vascular structure of theflow^er exhibits a definite advance upon that ol Aralia 

 in the direction of economy. Instead of the double peripheral series of bundles which 

 exists in Aralia, only a single series is present. By a further economical advance 



the peripheral bundles, which in Leycester 



lly equal to the sum of 



petals and stamens, are reduced to one-half the number in Viburnum, arriving at a 

 similar phase in the evolution of the vascular system of the flower to that attained by 



the Compositae. 



4. The Caprifoliace^e mark an advance upon the typical Araliaceae in the direction of 

 progressive loss of carpellary autonomy. The styles are united, except in Sambums 

 and Viburnum, Again, the synthetic development of the vascular system has led 

 to the disappearance in the body of the ovary of a distinct series of bundles corre- 

 sponding to the inner peripheral series of dorsal and lateral carpellary bundles that exists 

 in Aralia, Acanthopanax , and Sedera. This series is represented in the superior portion 

 of the ovary of Sambucus and Viburnum by strands which connect the ovarian bundles 

 with the stylar prolongations of the axial (marginal) bundles. But the connecting 

 strands are absent in Leycesteria and Lonicera, so that the final traces of the dorsal 



bundles have disappeared. 



5. The ovules of the Caprifoliacese are similar in structure, and take up a tangential 

 position in the loculus. This position is unaffected by abortion. In Symphoricarpus, 

 however, the lowermost sterile ovule in each pluriovulate loculus is radially situated, 



the raphe being abaxial. 



6. The morphology of the terminal seed in the Caprifoliaceae is rendered somewhat 

 obscure, owing to abortion and sterilization in the ovary. The seed is axially suspended in 

 Sambucus^smd is in this respect analogous to the lowermost ovules in the pluriovulate loculi 

 of Symyhoricarpiis, The seed, in Viburnum, has through abortion become displaced from 

 the axial position which it originally occupied to a parietal position. Since rudimentary 

 ovules occur immediately above the placental area of the seed, the latter also appears to 

 correspond to the lowermost member of a series, as in Sambucus. The seed produced 

 from the single ovule of the uniovulate loculus in Symphoricarpus may correspond to 

 the lowermost ovule of the pluriovulate loculi; but, if so, the fact is not evident, since 

 the parietal portion of the uniovulate carpels, perhaps owing to a sudden mutation, has 



