CORDAITEAE. 1 17 



in the pollen-chamber, a great and striking difference in size is at once 

 perceived ; the latter may be as much as a third larger than the others. 

 Again, the cell-mass formed inside the grain, which was much smaller than 

 the inner space of the grain in the anther, quite fills that space in the 

 grains found in the chamber and its cells have increased in number. If 

 this is indeed the general rule, the assumption of a subsequent further 

 development of the kind described above can scarcely be avoided. The 

 objection, that the pollen in the chamber is different from the pollen in the 

 anther, the two organs having belonged to two different species, would 

 explain the difference in size but leaves us still in a difficulty ; for in that 

 case we should expect to meet with the pollen of the chamber also lying 

 freely about in the pebbles, which does not appear to be the case. But now 

 that we know that the pollen-tube in recent Gyinnosperms does not proceed 

 from the internal cell-mass, the comparison of the process of development 

 in the two cases must at present be regarded as altogether obscure and 

 doubtful. 



It has already been incidentally remarked that casts of very various 

 form, named carpoliths, are objects of common occurrence in the Coal- 

 measures. These fossils would however be perfectly worthless from the 

 botanical point of view, if they were not also found in a silicified state in 

 the pebbles of Grand' Croix and in the carbonaceous nodules in seams of 

 coal. For that in all these cases we are dealing with the same remains 

 must be evident from their identity of form and from their mutual associa- 

 tion, especially when it is considered that the materials which have come 

 down to us, sometimes in the form of coal, sometimes as impressions 

 between slates, sometimes in a silicified or calcified condition, are all alike 

 vegetable remains from ground once covered by forests. We are indebted 

 for searching investigation into the remains of fructifications represented by 

 the carpoliths to Hooker and Binney 1 , and Williamson 2 , and above all to 

 the prolonged researches of A. Brongniart 3 . Now that all the various seeds 

 which have been examined have proved without exception to be seeds of 

 Gymnosperms, we may with great probability assume that all carpoliths 

 from the Coal-measures are remains of Gymnosperms. But since the 

 Cordaiteae are now acknowledged to be a highly differentiated division of 

 the series of Gymnosperms, it is equally probable that many of the carpo- 

 liths, which are found moreover in the same deposits with Cordaiteae, are 

 also remains of these plants. Impressions of carpoliths have in several cases 

 been found in connection with those of leafy branches, but this point will be 

 noticed again at greater length at the end of this chapter. Other carpoliths 

 again may be seeds of Conifers or Cycads, or may even prove to belong to 



Hooker and Binney (1). 3 Williamson (1), vm. 3 Brongniart (6). 



