386 Stiles .— The Structure of the Aerial Shoots of 
7. The sporophyll is probably homologous with a foliage leaf. The 
evidence is insufficient to decide whether the sporangiophore is foliar in 
nature or is an organ sui generis. 
8. The Psilotales are probably allied to the Sphenophyllales and 
Lycopodiales, but show greater resemblances to the former. 
Botany School, Cambridge. 
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