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THE AMERICAN NATURALIST 



[Vol. XLI 



very remotely connected with the Abietinese. Their pecuhar pro- 

 thalHal developments represent an apparently cenogenetic super- 

 addition to the primitive type of coniferous microgametophyte 

 found in the Abietinese. If this view be taken of the position 

 of the Podocarpineae, it may well be extended to the Araucari- 

 neae which present a similar microgametophytic development, 

 although it would take us too far afield and would involve the 

 discussion of yet unpublished data in regard to living and fossil 

 Coniferales, to defend that proposition in the present connection. 



Summary 



1. The Podocarpineae as represented by the genera Podocarpus 

 and Dacrydium are characterized by a proliferation of the two 

 original prothallial cells through more or less numerous anticlinal 

 divisions. 



2. The anticlinal proliferation of the prothallial cells in some 

 cases is accompanied by a similar proliferation of the generative 

 cell, an abnormality which appears to have been described in no 

 other Gymnosperms. 



3. Similar proliferation of the two original prothallial cells 

 has been observed in the araucarian genus Agathis. 



4. The proliferation of the two prothallial cells in the Podocar- 

 pineae and Araucarineae and the proliferation of the generative 

 cell in certain species of Podocarpus, cannot be regarded as a 

 primitive feature. 



5. The ground plan of microgametophytic development found 

 in the Podocarpineae and Araucarinea? points to their derivation 

 from an ancestral stock allied to the Abietineae. 



6. Since the Podocarpineae and Araucarineae present many 

 features of similarity in general habit, in geographical distribution, 

 in the organization of their megasporophylls, and the development 

 of their microgametophytes, it seems not improbable that they 

 are somewhat more nearly allied than has been supposed. 



