TRANSACTIONS OF SECTION K. 585 



growth was very feeble, whilst the boiled extract, although slightly retarding 

 germination at first, soon appeared to benefit the seedlings which became stronger 

 and healthier than those grown without extract. 



The extract was also found to have a marked influence on the growth of 

 certain soil organisms. It stimulated the growth of denitrifying bacteria, and 

 inhibited the growth of the nitrogen fixing bacteria. Both these effects were 

 destroyed by boiling the extract. 



4. The Polyphylctic Origin of Cornacece. By A. S. Horne, B.Sc, F.G.S. 



This conception of the phylogeny of Cornaceaa has resulted from a detailed 

 study of the structure of the flower of several genera of Cornaceae and a com- 

 parative study of the effects brought about by progressive sterilisation and 

 reduction in the ovary of the Caprifoliaceae, R'amamelidaceas, and Araliaceaa. 



A series may be found among Capri foliacese showing every intermediate stage 

 in reduction between ovaries of the Leycesteria type (double rows of ovules in each 

 chamber) and uniovular ovaries (Viburnum). The changes exemplified by this 

 series are accompanied by alterations in the vascular structure of the ovary 

 (Viburnum) and by modifications in the vascular supply to the ovule (Symplmri- 

 carpus). Progressive reduction trends towards the uniovular Condition, but each 

 genus pursues an independent course of development towards this condition 

 (Lnnicera, Symphoricarpus, Viburnum, Sambucus). 



The terminal ovules of Aralia, Davidia, and Viburnum have had, in each case, 

 a separate evolutionary history. 



The flowers of Cornaceae possess certain general resemblances, such as, for 

 instance, with respect to polypetaly, epigyny, &c, whilst the ovaries or loculi of 

 a number of genera are uniovular with terminal ovules. They possess, however, 

 peculiarities with regard to (a) structure of the ovary (Cornus) ; (b) vascular 

 structure of the ovary (Garrya) ; (c) vascular supply to the ovule (Grisclinia) ; 

 (d) form of ovule (Davidia) ; (e) structure of nucellus [Aucuba) ; (/) vascular 

 rudiments (Aucuba). 



It is suggested that these peculiarities indicate different origins. The general 

 resemblances in structure do not appear to be of any considerable value in 

 establishing cZo.se relationships within the order, but, on the other hand, are to be 

 regarded as striking parallelisms brought about as a result of the operation of 

 similar evolutionary processes upon distantly related forms. 



5. The Chromosomes of the Hybrid Primula kewensis. By Miss L. Digby. 



Much attention has of late been directed upon the cytology of hybrids, for 

 the behaviour of the nuclei of offspring derived from the union of unlike parental 

 germ cells may one day throw some light on the great unsolved problem of 

 heredity. 



As the hybrid, P. kewensis, has so interesting a horticultural history, it 

 seemed that a record of its cytology might be of value. The investigation has 

 proved both easy and productive, as the nuclear phases are clear and well defined, 

 and the chromosome numbers are low. 



The original P. kewensis plant appeared among a pure batch of P. floribunda 

 seedlings at Kew in 1899. It was noticeable on account of its more robust 

 growth, and its different foliage, and was believed to be a cross between P. flori- 

 bunda and P. verticillata. This supposition was verified the following year, when 

 the cross was made artificially, and resulted in a good proportion of P. kewensis 

 seedlings. The hybrid, P. kewensis, proved to be sterile, and bore only ' thrum- 

 eyed ' flowers. 



Some years_ afterwards in Messrs. Veitch's nurseries a single 'pin-eyed' 

 flower was noticed. This was promptly fertilised, good seed was set, and the 

 resultant plants possessed both ' thrum-eyed ' and ' pin-eyed ' flowers, and were 

 fertile. Thus the whole fertile, or seedling, stock of P. kewensis owes its origin 

 to the one ' pin-eyed ' flower on the sterile, or type stock of P. kewensis. 

 Messrs. Veitch have since, by selection, produced the variety, P. kewensis 

 farinosa, which accentuates the mealiness of the parent, P. verticillata. 



