268 ME. A. S. HORNE — A CONTEIBUTION TO 



Baillon *, wlio was undoubtedly influenced by bis researcbes f on tbe organogeny of 

 the flower in tbe Amentifera3, postulated a closer affinity. He bad discovered that tbe 

 ovary in Quercus^ Betula, and Castanea^ w^bicb is at first unilocular, becomes ultimately 

 multilocular, owing to tbe slow inward or centripetal growth of tbe parietal placentae, 

 and compared the development of tbe ovary in Castanea with that in Terminalia, a 

 genus of Combretaceae. Moreover, Payer \, in describing tbe growth of tbe terminal 

 placentae in tbe latter family, had already demonstrated their parietal and centripetal 

 nature. Baillon, accordingly and not unwisely, conceived the origin of the bilocular 

 ovary in lfarZ^« from tbe unilocular ^Z«w^i«m, supposing tliat the tendency towards 

 centripetal development exhibited by the Combretaceae bad advanced further in 

 Akmgium and Marlea. He then inferred that a close affinity existed between tbe 

 Combretaceae and the Alangiese, and literally swept the Alangieae into the 

 Combretaceae. 



Endlicber §, in 1847, discarded the idea of Combretacean affinity and transferred the 

 Alangieae to the CornaceaB. Clarke 1|, in 1850, from his comparative study of Marlea 

 and Cornm, advocated a very close affinity with tbe latter genus, stating that there 

 is but little left to distinguish tbe Alangieae and Cornaceae. The view of Cornacean 

 affinity held almost general acceptance until the advent of Wangerin's paper ^ ; 

 with this, tbe balance again inclines to the Combretacea3. Engler at first accepted 

 tbe opinions of Harms «*, but later ff brings tbe Alangiace^e into juxtaposition with 

 the Nyssaceae between the Rhizophoracese and Combretace^ in the Myrtiflorje. 



The facts accruing from this investigation do not, in the writer's opinion, favour one 

 side more than the other. Baillon's hypothesis is plainly untenable for the following 

 reasons:— Only one placenta is present in tbe ovary when unilocular, not two ; the ovary- 

 wall is much thicker on one side than on the other, leading to the expectation that a 

 loculus has failed to develop; and, finally, the infra-locular vascular tissue, under the 

 circumstances already discussed by the writer, suggests an originally axial or septal 

 extension. The evidence, on the contrary, shows conclusively that tbe ovary is reduced. 



Altbough 3Iarlea agrees with Cormis in the placentation'and orientation of tbe ovule, 

 the resemblance between them is less close than Clarke supposed, and even the styles 

 possess distinctive cbaracters ; tbe vascular systems, too, are dissimilar. 



A thorough comparison cannot be made until tbe structure of the ovule and nucellus 

 in Ilarlea is better understood. 



* H. Baillon in Adansonia, xii. (Castaneacees), 1-20. 

 t H. Baillon In Adansonia, xi. (Corylees), 163. 



+ 



J. B. Payer, Traite d'organogenie compare'e de la fleur (1854-1857) 

 § S. Endlicher, Gen. Suppl. iv. part iii. 17 (1847). 



% W. Wanfferin 



(18 



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

 ft A. Engler, Syll der Pfl. ed. VI. 179 (1909). 



