A'o. 486] 



PODOCARPlXK.i: 



sperm-cell in the Araucarineje sup{)lies another ariruineiit a<;aiii.st 

 their being more primitive than the other Coniferales. Their su- 

 perior antiquity further does not rest on any sound paljeonto- 

 logical Imsis, for so competent an authority as Schenk (Zittel's 

 Handbuch) remarks that if more abundant and more ancient 

 geological occurrence were to be considered as a criterion (.f anti- 

 quity, the Araucarineie must yield place to the 'ra\o(lin( a'. It 

 appears not unlikely, especially in view of observations made l)y 

 one of us on Mesozoic Coniferales, shortly to be published, that 

 the ' protosiphonogamic ' method of fertilization which is the inter- 

 esting discovery of ]\Ir. Thomson, is correlated with the prolifera- 

 tion of the prothallial cells in the Araucarineje, since the greater 

 length of pollen tube, in the absence of any special conductive 

 tissue such as is found in the Aii>:iosj)erni.s, calls for a greater 

 development of prothallial tissue. The failure of the pollen to 

 reach the micropyle, on the other hand, may have been due to the 

 unfavorable inihieiu t' of drought upon the fluid secretion which in 

 other ( oiiifcrs Hoats tlie pollen to the micropyle. 



Turning from the Araucarineje to the Podocarpinea\ we find 

 \(^ry similar conditions in regard to the prothallial j)rolifi'ration-. 

 The plan of prothallial development here as in the Al)i(>tinra' and 

 Araucarineiv involves two prothallial cells, but as in the Arau- 



tion. That this i> the n-ue view <.f the matter is rcn.lclvd more 

 prol.al.lr by the fact that even the gcn.>rativc cell may be albvt.T 



jrrnnj-lu nuA P \larr;idloidrs, <\vsvv\W^ above, ^'bhere i'. <.er- 

 tainly no reason from our knowle.lge of the older and zoi.lo- 



