128 



SCIENTIFIC AGRICULTURE 



December. 1921. 



the central vein of a leaflet, one of the 

 original lateral veins becoming the cen- 

 tral vein of the new and supernnmerary 

 leaflet. In the second case the splitting 

 takes place through the centre^or median, 

 of the original central vein of a leaflet. 

 In either case the splitting may manifest 

 itself differently, depending on, what 

 .stage of development of the embryonic 

 leaflet it takes place. If it takes place 

 very early, new and independent leaf- 

 lets are originated, the result being an 

 increase in the normal number of leai- 

 lets. If it takes place at a comparatively 

 late stage of development, the result is 

 that more or less deeply cleft leaflets 

 occur. 



The development of polyphyllous leaves 

 is often connected with the so-called fascia- 

 tion, i.e., the broadening and flattening 

 of either the stems or the pedicels, or 

 both. In such cases a marked increase in 

 the number of the fibro-vascular bundles 

 has been observed (Kajamis 4), which in 

 turn may favor not only the <levelopment 

 of supernumerary leaflets, but also the 

 development of whole supernumerary 

 leaves. Polyphylly is, indeed, regarded 

 by Kajamis as a mere form of fasciation, 

 as are also certain other anomalies such 

 as "trumpet" shaped leaflets for instance. 



Inheritance of Polyphylly:— The na- 

 ture of polvphvllv was first thoroughly 

 studied by de Vries (2. pp. 435-449). In 

 1886 de Vries found two red clover plants 

 which had several 4-foliate leaves and one 

 5-foliate. In the progeny of these plants, 

 represented by a little over one hundred 

 individuals, about fifty per cent of the 

 plants were found to produce at least one 

 4-foliate leaf. By selecting and propagat- 

 ing four of the plants showing polyphyl- 

 lous tendencies de Vries obtained in the 

 next generation an increased number of 

 pol\phyllous plants, nearly 80 per cent, 

 of the progeny having one or more 4- 

 foliate leaves. By repeated selection 

 through six generations de Vries finally 

 succeeded in developing or rather isolat- 

 ing a distinct variety which he called 

 Trifolium pratense qiiinqiiefolium. It is 

 characterized by having leaflets varying 

 in number from four to seven around a 

 mean of five. 



Dc Vries ascribes the development of 



polyphyllous leaves in his variety to the 

 existence of a latent or semi-latent char- 

 acter which manifests its presence parti- 

 cularly under favorable conditions of life. 

 In explaining the presence of this latent 

 or semilatent character de Vries bases his 

 contention on the supposition that the re- 

 mote ancestors of the clovers had pin- 

 nate leaves, a view which is sliared by 

 other botanists and is supported by, 

 among other things, the appearance, now 

 and then, of true pinnate leaves instead 

 of the ordinary multifoliate ones. If this 

 contention is correct, i.e., if the trifoliate 

 leaves of the clovers are derived from 

 Leguminosae Avith pinnate ones, the 

 phenomenon of polyphylly must evidently 

 be regarded as an atavistic one. This 

 tendency to atavism may be intensified. 

 so to speak, under favorable conditions. 

 Thus, de Vries found that the better the 

 seeds are nourished on the parent plant 

 the more prominent becomes the develop- 

 ment of polyphyllic leaves in the individ- 

 uals produced by them. 



In explaining the inherent nature of 

 polyphylly, Kajamis at first (1. p. 69-70) 

 endeavored to explain the appearance of 

 polyphylly in Mendelian terms.' Like de 

 Vries, he as^iumed that the trifoliate 

 clovers have been developed from ances- 

 tors having pinnate leaves. He attributed 

 the original reduction of the number of 

 leaflets to the development of inhibition 

 factors which, as long as they are func- 

 tioning normally, keep down the number 

 of leaflets to three. Should, however, for 

 some reason or other, the vigor of the in- 

 hibition factors become impaired, the re- 

 sult would be the appearance of polyphyl- 

 lous plants. Such plants would produce 

 equal numbers of egg cells and pollen cells 

 with and without inhibition factors. Con- 

 sequently, seed developed by such plants 

 after fertilization by pollen from normal 

 plants Avould theoretically produce fiftA 

 ])er cent polyphyllous heterozygotes an^I 

 fifty per cent normal homozygotes. 

 Kajamis finds support for this theory in 

 the fact that he received, after open- fer- 

 tilization of the first polyphyllous plant 

 secured, 71 polyphyllous ones and 60 nor- 

 mal ones, the theoretical figures being 

 65.5 for each. 



As a result of further investigations. 



