Experimental and Analytical Studies of Pteridophytes: XXI. Investigations on Marsilea

An account is given of the effects of various concentrationsof glucose, sucrose, and fructose on the development and morphologyof aseptic cultures of Marsilea sporelings. The response ofthe sporelings to a range of different sugars and to growthin liquid or on solid media is also described. The results are discussed with special reference to the relationshipbetween nutrition and heteroblastic leaf development. Otheraspects of the influence of various sugars on the growth ofplants in aseptic culture are considered in relation to theexisting literature.     

Experimental and Analytical Studies of Pteridophytes: XIX. Investigations on Marsilea

It is shown that in plants of Marsilea growing in aseptic culturereversion to juvenile leaves may be obtained by depriving thecultures of either sugar or mineral nutrients. Reduction toa protstele and other anatomical observations are also described. Juvenile leaves were produced by excised spices of mature plants,and by lateral branches developing on feeble decapitated plants.The problem of heteroblastic development is discused in relationto these and other observations.     

The Morphology of Protonema and Bud Formation in the Bryales

The development of protonema from spore in aseptic culture wasfollowed in species representing 14 genera and 7 orders of theBryales. In no case could a distinction be made between sharplydefined ‘chloronema’ and ‘caulonema’stages. In all species, with the exception of the anomalous Cinclidotusfontinaloides, the protonema developed a markedly heterotrichoushabit, with prostrate filaments of relatively unlimited growthand erect filaments of more restricted development. The twotypes of filament were usually distinct in cellular characteristicsas well as in the direction of growth. In some cultures a thirdtype of filament grew downwards into the medium. Shoot buds were found to occupy diverse positions in differentspecies, but the commonest position was near the base of a primaryfilament of the erect branch system. Shoot buds were formedas readily in artificial light of sufficient intensity as innatural daylight.