140 



MORPHOLOGY OF SPERMATOPHYTBS 



ovules are evidently cauline, being borne at the summit of a short 

 bractlet-bearing shoot, which arises from the axil of a bract. As 

 has been mentioned before, the ovules may be reduced to a soli- 

 tary one in a strobilus, and the bracts may be very few in num- 

 ber. Two envelops are ap- 

 parent, and permit the 

 same diversity of opinion as 

 exists in reference to the 

 ovular envelops in the Gne- 

 tales. It seems altogether 

 simpler to regard the two 

 envelops in Cordaites as 

 two integuments, although 

 there is no tubular pro- 

 longation of the inner in- 

 tegument as in the Gne- 

 tales. The nucellus devel- 

 ops a remarkably promi- 

 nent and persistent beak, 

 composed of modified and 

 heavy-walled cells, through 

 which a passageway leads 

 to a large pollen chamber 

 (Fig. 96). The whole 

 structure of the nucellus 

 recalls the Cveads and 

 Ginkgo, and, as is the case 

 with them, the nucellar tissue which caps the embryo sac 

 disorganizes, permitting the persistent beak to settle down 

 upon the embryo sac (Fig. 91). There is also a striking 

 resemblance to the nucellus of Ginkgo, as described by Hirase, 

 in the fact that the endosperm develops a protuberance which 

 supports the settling beak like a " tent-pole." Under the shel- 

 ter of this improvised tent the archegonia are found and the 

 male cells are discharged. The situation is so suggestive of 

 Oycads and of Ginkgo that one can hardly escape the conviction 

 that in the process of fertilization they are approximately the 

 same. Traces of the archegonia have been found, so that their 

 position is definitely determined. 



The ovulate structures of the Cordaitales as described above 



Fig. 96. — CordiantJms Grand? Eiiri/i, showing 

 the beak of the nucellus ; wedged in the pas- 

 sagewaj' are the large pollen grains, which 

 show the shagreenlike surface and the in- 

 ternal group of cells. — After Renault. 



