INDUCED APOGAMY 



It would be a matter of considerable interest to be able to examine cytologically some 

 freshly collected wild examples of the species, since the history of cultivated plants is such 

 that it would be unwise to exclude the possibility that hybridization and subsequent 

 chromosome doubling may have occurred in a botanic garden and not be a specific 

 attribute of Z). caudata in the wild state. Until this can be done it is scarcely profitable to 

 study these plants in greater detail. These results are nevertheless of interest in showing, 

 first, how an unsuspected hybrid can be detected by a technical method different from 

 those previously employed. Secondly, it is perhaps appropriate to notice that had any of 



Fig. 206. Meiosis in Doodia caudata (Cav.) R.Br, from sections, x 1000. a. Sexually produced plant 

 with regular pairing, b. Apogamously produced plant with many lagging univalents but also 

 some pairs. 



the spores borne by the apogamously produced plant been viable, which under certain 

 conditions might conceivably occur, this species might have given one of the rare 

 examples of an experimental series advancing in the direction of diminudon of chromo- 

 somes. The fact that this possibility has not been realized, though expectation has been 

 brought near enough for it to seem conceivable, brings out very clearly the relative irre- 

 versibiHty of most types of polyploidy hitherto encountered, and this irreversibility, 

 whatever its cause, is undoubtedly a fact of evolutionary importance. 



Before leaving Doodia it may be worth mentioning in passing that Dr Duncan's results 

 on apospory were also repeated by Mr Ashby, though less attention was given to these 

 and the plants have not been cultivated to maturity. The consequence of inducing 

 apospory in an apogamously produced plant is, of course, merely to return again to a 

 normal prothallus. The consequence of inducing apospory in a normal young plant is 

 the production of a polyploid prothallus. One such prothallus after self-fertilizadon gave 

 a sporophyte, in the roots of which over 200 chromosomes were counted. Since twice 



203 



