QUANTITATIVE INFLUENCE OF CORRELATION 213 



If a plant should form no reproductive organs but exhibit a luxuriant 

 vegetative growth, the latter may be either the cause or the consequence of 

 the suppression of the reproductive organs. Both cases occur. 



In illustration of the former I may quote the behaviour of many water- 

 plants which, like species of Marsilia, Riccia fluitans, and others, do not 

 form their reproductive organs so long as the external conditions are 

 favourable for growth, but should they grow as land-plants the luxuriance 

 of the vegetative development is restricted and the reproductive organs 

 arise normally. H. Muller l has also conjectured that the explanation of 

 the fact that plants which shoot in a higher temperature than normal often 

 produce ' blind ' flowers may be found in the leafy shoots depriving the 

 flower-buds of nourishment. A similar explanation may be given of the 

 frequent cases in which the formation of seed is arrested ; in Lilium 

 candidum, for example, seeds are never formed ; in plants like Ranunculus 

 Ficaria provided with means of vegetative propagation seeds are seldom 

 produced. More than two hundred years ago K. Gesner showed that 

 flower-stems cut off from Lilium produced seeds 2 ; in the normal condition 

 the seed-formation is hindered because the plastic material which might be 

 used for the seeds streams into the bulb where it is turned to account in the 

 formation of bulbils for asexual reproduction. In Lachenalia luteola 

 also Lindemuth 3 found that notwithstanding artificial pollination no 

 seeds were formed, but that their production could be brought about 

 by cutting off the flower-stalks ; and Van den Born 4 has proved the same 

 in Ranunculus Ficaria. 



The opposite case that an increase of vegetative development is 

 a consequence of the suppression of the reproductive organs or of their 

 incomplete development is illustrated in many double-flowered plants. 

 In the vicinity of Munich, Cardamine pratensis occurs abundantly with 

 double flowers. The plant multiplies copiously by buds which are deve- 

 loped upon the basal leaves and out of the apex of the double flowers, 

 and thereby this bud-bearing form which has entirely lost seed-formation 5 

 has partly replaced the normal seed-forming plant a condition of things 

 which could only be possible in a climate with so great a rainfall 

 as that of the high plain of Upper Bavaria. The example of Isoetes 



1 H. Muller, Beitrag zur Erklarung der Ruheperiode der Pflanzen, in Landwirtsch. Jahrb., 1886. 



2 See Jost, in Botan. Zeitung, 1897, p. 17. 



3 Lindemuth, Uber Samenbildung an abgeschnittenen Blutenstanden einiger sonst sterilen Pflanzen- 

 arten, in Ber. der deutsch. Botan. Gesellsch. xiv (1896), p. 244. 



1 Van den Born has induced the development of fruit in Lilium candidum and in Ranunculus 

 Ficaria by removing from the former the bulb-scales and from the latter the small basilar tubercles. 

 See La Belgique Horticole, 1863, p. 226. 



5 Adventitious shoots may be formed also on the normal form, but the absence of seed-formation 

 sets free a larger amount of plastic material. 



