INDUCED APOGAMY 



was the spasmodic appearance here and there in a culture pan of small groups of pale- 

 coloured sporangia borne on the upper surface of some though never on all the prothalli, 

 and at a later stage these were followed by the apogamous development of other organs 

 from different parts of the prothalli. 



The residual material remaining from Lang's work consisted of a number of adult 

 sexually produced sporophytes of the strain and one old culture pan of prothalli, which 

 had, however, apparently ceased to produce sporangia. In order to rejuvenate the pro- 

 thallial material fresh spores of the strain obtained from one of the descendants of the 

 original plant were sown in 1943 and kept away from free water for over a year. Late in 



Fig. 208. Sexual and apogamous Scolopendrium vulgare Sm. a. Sister plants of the same age, of the horti- 

 cultural strain used, the larger plant produced sexually, the smaller apogamously. About one-third 

 natural size. b. Root-tip cell of a sexually produced plant from a section, x 1000. c. Root-tip 

 cell of an apogamously produced plant from a section, x 1000. 



1944 the first signs of apogamy were encountered, including both apogamous buds and 

 sporangia on prothalli, and their production continued sparingly during 1945 when 

 observation ceased. During this time one group of sporangia was successfully sectioned 

 by Mr Ashby and meiosis in it encountered, while other specimens of apogamous out- 

 growths were lifted from the pan and grown on. One complete plant obtained in this 

 way survived for long enough to give the photograph of Fig. 208, which was taken in the 

 autumn of 1 945. This plant was sparingly fertile for the first time in that year, producing 

 two diminutive sori, both of which were used for cytological purposes, after which the 

 plant unfortunately died. 



The relative difference of size between a sexually produced and an apogamously pro- 

 duced plant of equal age of this strain o^ Scolopendrium is clearly shown by Fig. 208 a. In 

 the younger stages the difference is still more marked, the organs of apogamously pro- 

 duced plants being so small and delicate that they are difficult to handle. As expected, 

 the cytological basis for this difference of size lies in difference of chromosome number. 

 The sexually produced plants, in spite of their ramo-furcate and other qualities, have the 

 normal chromosome number of the wild species and show 72 chromosomes in their roots 



205 



