ANGIOSPEKMS 



341 



the fern to the angiosperm, until it has reached its limit in 

 the slender filament of the angiosperm stamen. With this grad- 

 ual reduction in size its original chlorophyll tissue has been lost, 

 together with its power of making starch, so that the microsporo- 

 phyll now serves a single function, namely, that of producing 



Microsporophylls Microsporophyl 



Micro- 

 sporangici 



Micro - 

 sporangia 



Megasporophylls 



_Mega- 

 '/sporancjid 



Fig. 201. Diagram illustrating the homologous, or corresponding, parts of the 

 sporophylls and sporangia of the higher spore and seed plants 



, pinnule (sporophyll) and sporangium of the maidenhair fern ; 6, microsporophyll 

 and microsporangium of Selaginella ; c, d, corresponding parts of the anthers of 

 the spruce and of the marsh marigold ; e, pinnule (sporophyll) and sporangium of the 

 maidenhair fern; /, megasporophyll and megasporangium of Selaginella; g, ovu- 

 lif erous scale and ovules of the spruce ; h , ovary and ovules of the marsh marigold 



microspores, instead of the double function of spore production 

 and photosynthesis, as in the ferns. The sporangia have also 

 become transformed from the simple, distinct sporangia of the 

 ferns .into the four united microsporangia of the angiosperms, 

 borne .on a single sporophyll. 



The pistil, which may be composed of a single megasporophyll, as 

 in the, marsh marigold, or of several megasporophylls, as in the lily 

 or the apple, represents a still greater transformation in sporophyll 



