302 



GYMNOSPERMS 



gin can be traced, it is hypodermal. In Taxus, the archesporial cell, 

 or cells, are hypodermal, and can be recognized very easily by the 

 deep staining; and, later, the line of cells between the mother-cell 

 and the periphery is very easily traced (fig. 307^4,5). In Taxus sev- 



/4 



Fig. 307. — Archesporium and spore mother-cells of conifers: A and B, Taxus bac- 

 cata: A, single archesporial cell; B, two archesporial cells have divided, giving rise to 

 two tapetal cells and two primary sporogenous cells, which are also the mcgasporc 

 mother-cells; C, Ketelceria fortunei, megaspore mother-cell; D, Larix europea, longitudi- 

 nal section, young ovule showing megaspore mother-cell; E, Pinus rigida, deeply placed 

 megaspore mother-cell; A and B, after Dupler,"* X238; C, after Hutchinson.^t* 

 D, after Strasburger,'*'" X 141 ; £, after Margaret Ferguson,'" X46. 



eral mother-cells may divide, and several megasporcs may germi- 

 nate, producing gametophytes which may reach an advanced free 

 nuclear stage. In Ketelceria, a peculiar Chinese gymnosperm, which 

 has been variously assigned to Pinus, Abies, and Tsuga, the mother- 

 cell is sharply marked (fig. 307 C). Perhaps the earliest form in 



