THE STUDY OF THE EVOLUTION OF THE TLOWEE. 243 



tliat the ovary of Quercus, Castanea, and other genera becomes multilocular during 

 development, owing to tlie inward or centripetal growth of the parietal placentae, and, 

 hence, was led to the belief that the bilocular ovaries found in certain genera of 

 Cornaceae originated from unilocular types. But the ovary, in Cornacese, as will be 

 subsequently shown, has advanced beyond the evolutionary phase described by Baillon 

 for the Amentiferse, and presents instead advanced stages in progressive abortion. 



Harms * brings together the largest grouping of genera ever included in the 

 Cornaceae. He asserts that intermediate forms exist between ovules of the dorsal and 

 ventral types, and hence there is no adequate reason for excluding genera with the 

 Aralian type of ovule {Nyssa and Davidia) from the Cornaceae. But Harms's opinions 

 carry little weight, owing to the fact that the criteria upon which he relies are 

 insufficient to express the diverse structural forms of ovule obtaining in this family, 

 ' Walther Wangerin f contributed a lengthy paper, entitled "Die TJmgrenzung und 

 Gliederung der Cornaceae," to Englcr's ' Jahrbiicher,' in 1906. This paper describes in 

 detail the chief morphological and anatomical characters of the family, gathered from 

 the works of Sertorius, Baillon, and others, and from an examination of herbarium 

 material. This paper forms the basis of Wangerin's monograph | contributed to ' Das 



Pflanzenreich 



The Cornaceae of Harms are, in this monograph, resolved 



four old families, the Garry aceae, Alangiaceae, Nyssacese, and Cornaceae. Two of these, 

 the Nyssacese {Nyssa and Dacidia) and Alangiaceae, according to Wangerin, are 

 distinguished by two integuments. The i3resent author §, however, recorded only a 

 single integument for Dacidia in 1909, and is now able to show that Nyssa also is 

 unitegumentary. Hence Wangerin has relied upon a morphological error with 

 regard to the Nyssace^e, and, in consequence, has failed to present a convincing case 

 for the re-establishment of both families. 



The present investigation reveals several hitherto-unrecorded details in the floral 

 organization, the special morphology of the ovary and ovule, and the course of the 

 vascular tissue in the families under consideration. A striking evolutionary series has 



n 



been traced in the Caprifoliaceae, where, owing to progressive abortion, the parietal 

 portion of the ovary that is well represented in Leycesteria has b(?come reduced until, in 

 Samhucris, only vestiges remain. Progressive abortion, in the Caprifoliaceae, is accom- 

 panied by progressive sterilization— the ovules are not only reduced in number, but 

 transitional stages occur from ovules physiologically sterile to be found in Lonicera to 

 the merest rudiments discovered in Samhucus. Owing to reduction the ovary or loculus, 

 in several genera, becomes monospermous, with a terminal seed, but in each case the 

 one-seeded condition has been attained by a different method. Comparison with an 

 analogous sterilization series in the Hamamelidaceae shows that the terminal seed in the 

 Caprifoliaceae is constantly axially suspended, or in the exceptional case of Viburnum 

 axially borne by origin, whereas in the latter family it is situated parietally. 



* Harms in Engl. u. Prantl, Nat. Pfl., Teil iii. Abt. 8. 

 t W. Wangerin in Engl. Bot. Jalirb. Baud xxxviii. Heft 2 (1906). 

 X W. Wangerin in Engl. Das Pflanzenreich, Heft 41 (1910), 

 § A. S. Home in Trans. Liun. Soc. ser. 2, Bot. vii. (1909) 323. 



