554 THE GENESIS OF NEW FORMS AS A RESULT- OF CROSSING. 



following year the gall-mites settled on the latter also, and the greater part of their 

 flowers then became double. The same result was obtained after living gall-mites 

 were transferred by me to isolated plants of Veronica officinalis with single 

 flowers. These in the following year also bore some double flowers. Fruits with 

 ripe seeds were only produced from the flowers which had remained single amongst 

 the double ones; and the plants which grew up from these seeds always bore single 

 flowers only. The gall-mites disappeared for some unascertained reason — probably 

 they died in the winter. Veronica officinalis has only two stamens in each flower 

 and in the double flowers both these and the two carpels are changed into petals 

 so that of course we could not expect fruit and seeds from them. It would not 

 be impossible, however, that flowers of other plant families which are provided 

 with a large number of stamens might behave difierently. It might happen, 

 for example, that only some of the stamens would be changed into petals by the 

 gall-mites, and that the carpels would remain capable of fertilization. If on such 

 plants fruits and seeds capable of germination should ripen, the latter might 

 perhaps produce plants with completely and half double flowers. This would be 

 explained by supposing that the alteration undergone by the protoplasm of the cells 

 in the outer part of the flower had extended to the inner, especially to the ovules 

 and seeds, and further to the plants proceeding from these seeds. I would there- - 

 fore not undertake to state that the Stocks (Matthiola annua and incana), the 

 Wallflower {Cheiranthus Gheiri), the Pinks (Dianthus Caryophyllus, plumarius, 

 &c.), the Poppies (Papaver Rhoeas and somniferum), various Eanunculacese 

 {Delphinium, Pceonia, Ranunculus), and many other plants which have long been 

 cultivated in gardens with semi-double flowers, and which produce such flowers 

 when propagated by seeds, had not gained this characteristic in the first place 

 by the influence of gall-mites. It is less probable, though not beyond the range 

 of possibility, that by the grafting of Hawthorn branches whose uppermost leaves 

 have been deeply segmented by the influence of the gall-gnat Gecidomyia Grataegi, 

 a Hawthorn bush might be produced which would exhibit these deep segmentations 

 and slits on all its foliage. However, these last remarks are the merest suppositions; 

 at present we have not the data on which to base any definite conclusions. 



THE GENESIS OF NEW FORMS AS A RESULT OF CROSSING. 



The aim of agriculturalists has always been so to cultivate their land as to rear 

 plants likely to grow luxuriantly, to bear good fruit, and thus to afibrd an abun- 

 dant harvest in return for their pains. Gardeners similarly have made it their 

 endeavour to produce from wild plants races whose flowers are superior to those 

 of the ancestral stock in form, colour, and scent; and the results of their labours 

 are the delight and admiration of all lovers of beauty. In both cases the idea has 

 been to perfect and "ennoble", and the means adopted have been successful to a 

 degree calculated to amaze anyone who studies the history of cultivated plants with 

 attention. The methods which led to these results have not always been deliber- 



