Lesquereux.] ^OO [Feb. 18, 



specimens, are the only of these families which are interesting to the bo- 

 tanical paleontology of this country. 



For the Cordaites, Prof Renault has given very detailed anatomical de- 

 scriptions and splendid illustrations of all the organs of these plants, as 

 complete indeed as if they liad been made from living vegetables. The 

 development of the plants is followed from the fertilization of the ovule ; 

 for grains of pollen have been discovered, by vertically cutting the em- 

 bryonic bodies, one already enclosed into the pollinic chamber, two of 

 them still on their way downward in the pollinic tube. 



The first of these grains is fully ripe, as recognized .by the author, who 

 has been enabled to see a difiereuce in the mode of fertilization from the 

 difference of size and structure of the grains of pollen which were as pro- 

 fusely disseminated around, at the Carboniferous epoch, as are those of the 

 Conifers at our time. When found in a state of dissemination, the grains 

 of pollen of the Cordaites are already a third larger than those still fixed to 

 the anthers, and they appear then composed of an internal globule (entine), 

 and of an outside envelope (extine). On the grains still placed in the pol- 

 linic tube, the fertilizing globule is more distinct, and more distinctly sepa- 

 rated from the envelope, while the grain placed in the pollinic chamber is 

 still larger, and its two parts more distinct. It seems therefore, according 

 to the remarks of the author, that in their exit from the anthers, the pol- 

 linic grains are not fully ripe or prepared for the act of fecundation, and 

 that they have need of a second process of evolution, while enclosed in the 

 pollinic chamber, for a full separation of the cells and the completion of the 

 fertilizing action. This process differs from what is remarked in the plants 

 of the present time, by the fact only, that now the pollinic grain is already 

 perfect, when it becomes detached from the anther, and is not surrounded 

 by a membrane. 



The wood of the trunks of Cordaites is composed of a thick pith or 

 medullary cylinder, which is generally known under the name of Artisia 

 or Sternbergia. The medullar cylinder very variable in thickness is 

 obscurely costate lengthwise and transversely marked by close parallel 

 furrows, sometimes anastomosing with each other. These furrows are 

 formed, as seen from the anatomical analysis of silicified branches, by 

 medullary transversal bands, which in the living plants, produced a divis- 

 ion of the medial cylinder into as many empty excavations, each corre- 

 sponding, by contraction of the surface, to an outside furrow. 



The wood itself is formed in its inside part, or in contact with the 

 medullary axis, of two zones ; the'inside of the first is composed of annulate 

 and spiral trachids, its outside of radiate and reticulate ones separated by 

 the medullary rays. The trachids of this last zone gradually pass, by the 

 enlarging of the striae of their walls, into punctate trachids, which constitute 

 a second woody zone, which is of considerable thickness in large trunks, 

 and always composed of trachids with areolate perforations, disposed in 

 radiating striae, and separated also by medullary rays. The areoles are in 

 contact ; by mutual compression they become hexagonal, and are pierced 



