HEILBORN, CYTOLOGY OF ANANAS SATIVUS LINDL. 5 



It is thus evident that the different races of Ananas 

 ativus must be of very different cytological constitution, 

 future investigations will probably reveal among these races 

 I, series of multiple chromosome numbers like those already 

 ound in many genera and, in addition, hybrids such as our 

 5anos-race. Probably there will be found within this species 

 ihromosome relations similar to those known to exist within 

 he genus Bosa (Täckholm 1920, Blm^kburn and Harrison 

 921). It is now important to realize that races of our 

 5anos-type are probably hybrids between other Ananas sativus- 

 aces, whereas races of our Tenguel-type are, apparently, no 

 lybrids at all. Hence the present writer finds it very un- 

 ikely that the species as a whole should be of hybrid origin. 



It appears from the foregoing that both the Tenguel-race 

 md the Banos-race are parthenocarpic. Hence it is clear 

 hat also races with good pollen — and thus, apparently, 

 lot of hybrid origin — may produce seedless fruits. We 

 Qay thus state that, on account of its reduction division, 

 inanas sativus cannot be cited as a proof of the hybrid- 

 ypothesis of parthenocarpy. The question of the origin 

 f Ananas sativus may, perhaps, be settled with certainty, 

 7hen a great many of its cultivated races have been 

 ivestigated cytologically. It should, however, be pointed 

 ut at once that Ananas sativus is a species unusually well 

 uited for studies on the origin of parthenocarpy, as it con- 

 ists of both races with good and with bad pollen. 



Again, it appears from the works of Tischler and 

 »'Angremond that all races of edible bananas {Musa sapi- 

 ntum) hitherto investigated have irregular reduction division 

 nd may thus be regarded as hybrids, whereas several other 

 pecies of Musa have been found to have normal reduction, 

 ^he edible bananas are parthenocarpic, the others are fertile, 

 lence it seems evident that the parthenocarpy in Musa sapien- 

 um must be of hybrid origin, although the details of the re- 

 uction division in that species are not yet fully worked out. 

 ,3 to Carica, the writer (1921) has recently pointed out the 

 ifficulty of drawing any decisive conclusions from cytological 

 r systematical studies. It could not be decided if the 

 •arthenocarpic species of Carica really are hybrids, though 

 hat possibility is certainly not excluded. 



