THE ABORTION OF OVULES 363 



liable to considerable variation. The number of seeds in a 

 pod varies from one to ten. 



The development of the seedless fruit has a most important The indica- 

 bearing on the relation between the form of many fruits and seedless 

 the failure of the ovule. The gerrriination of the pollen-tube, ^■■'"*- 

 writes Dr Jost in his Lectures on Plant Physiology (English 

 edition, 1907, p. 370), has an exciting influence on the develop- 

 ment of the fruit, so that fruits may be formed where de- 

 generate ovules fail to become seeds. Again, Dr PfeflFer writes 

 that the penetration of pollen-tubes may act as a stimulus to 

 growth of fruits without any fertilising influence being exercised 

 {Physiology of Plants, ii. 173). We have here a means of 

 explaining some of the curious forms of fruits. But nauch 

 will depend on whether the ovules habitually fail in the same 

 part of the young fruit, or whether their failure is occasional 

 and not restricted to one situation. In the first case we have 

 a persistent effect produced on the fruit's shape which requires 

 a specific or a generic value, as in Anemone. In the second we 

 have inconstant variation of the fruit's form, such as I have 

 described in the instance of Iris Pseudacorus. 



It would, however, be rash with the scanty data at my 

 disposal to push this view very far. Yet the ovules that fail 

 in a Primula or an Iris capsule appear to be in quite a different 

 category from the ovules that fail in the fruits of the Oak or 

 of the Coco-palm. In the first case it would seem that the 

 ovules were actually fertilised and afterwards aborted. In the 

 second case it would appear that the ovules were incapable of 

 being fertilised, since they persistently fail. Lord Avebury 

 would regard such persistently functionless ovules as carrying The 

 us back to the time when, in the ancestors of the plant, all the o™^e.°" *^* 

 ovules developed into seeds {Seedlings, Internat. Sci. Ser., pp. 

 241 and 243). Professor Bower holds a similar view with 

 reference to the abortive ovules in the beak of a fruit of 

 Anemone nemorosa, regarding them as "the imperfect repre- 

 sentatives of a plurality of ovules in the ancestry " {The Origin 

 of a Land-Flora, 1908, p. 127). It should, however, be pointed 



