304 



superficial covering of cells into a sporangium : if this were so , it 

 follows that we may recognise in the synangia or so called „coales- 

 cent sporangia" of the Marathiaceae, and also in the „sporangiophore" 

 of Ophioglossum , instances of the incomplete separation of the indi- 

 vidual sporangia, though the archespore in each is separate from that 

 of its neighbours. From a comparativ point of view I am disposed 

 to regard these synangia wich are found in more than one series of 

 the Vascular Cryptogams, as primitive in character, and as indicating 

 not a coalescence of sporangia whose distinct archesporial cells were 

 derived by isolation from some such united ancestral archesporium 

 as is seen in the Bryophyta of the present day. If such Eusporangiate 

 forms with synangial sori were the more primitive, it is not difficult 

 to conceive how in plants growing in moist and shaded positions, 

 where the danger of exposure to drought is minimised, the sporangia 

 might have become not only completely separate, but also reduced 

 in bulk, as we see in the progression through the Osmundaceae to 

 the truly Leptosporangiate Ferns : and parallel with this reduction 

 of the sporangium, as I have shown elsewhere, would have proceeded 

 the reduction in mass of all the other members of the sporophyte. 



Aus beiden Hypothesen ergibt sich fUr die Natur der sterilen 

 Farnblatter die gleiche Schlussfolgerung; es miissen niimlich in beiden 

 Fallen die sterilen Farnblatter urspriinglich fertil gewesen sein, und 

 batten somit erst im Laufe der Zeit die ihnen von Haus aus zukom- 

 mende Function der Sporenproduktion eingebiisst. Prantl bekennt 

 sich denn auch (11a p. 63) zu dieser Annahme, und ebcnso Bower, 

 bei dem es III p. 266 folgendermaassen heisst: 



„From it we recognise that the ascending series shows a pro- 

 gressive sterilisation of the tissues of the neutral generation, and also 

 an increasing elaboration of external form and internal structure, the 

 two lines of progress going, in a measure, hand in hand. 



„It is obvious that, if the progression were as above stated, the 

 function of the spore production preced the vegetative functions of 

 the sporophyte in point of time; spore -producing members may, in 

 this sense, be termed primary from the point of view of descent, and 

 the vegetative members, secondary; the morphology of spore produ- 

 cing members should accordingly take precedence of the morphology 

 of vegetative members." 



Die rrantl'sche und Bower'sche Hypothese steht einer an- 

 deren Auffassung gegenilber, die bisher wohl die meisten Vertreter 

 gefunden hat, und welche die fertilen Blatter der Fame als meta- 



