﻿i6o 



REPRODUCTIVE STRUCTURES. 



case, however, the characters were somewhat obscured by the state of preservation, 

 although there could be but little doubt as to the correctness of Solms' identifica- 

 tion. Later the writer published the text-figures here introduced (189), and noted 

 the close agreement between the cycadeoideau pollen and that of the living cycads. 

 In the various strobili from which the writer has cut sections, pollen has been 

 nearly always found in more or less perfect preservation. Every stage of distension 

 and desiccation is to be seen, and by searching one may, particularly in strobilus 

 No. 1 of specimen 214, find beautifully stained grains which are outlined as sharply 

 as in the case of preparations showing the pollen of living cycads. Such a grain is 

 shown in figure 83, No 19. The pollen of Cycadeoidea, while far smaller than that 

 of Cordaites, is significantly larger than that of the living cycads. Whether or not 







<£2> <3> C^ 



O Q O (q) 



C^ O Cp> 



C^ Q> O Q Q> 



Fig. 84. — Cycadeoidea dacotensis. 



Supposed structural markings on silicified pollen grains in sections 104, 1 10, and 314, cut from fructification I, T, 214. 



there was a distinct increase in the size of the pollen grain at the time of fertilization 

 as in Cordaites is as yet unknown, since no section of seeds yet cut traverses a 

 pollen chamber containing pollen grains, although such are likely to be obtained 

 in the course of future study. But obviously the cycadeoideau pollen may have 

 normally passed through several months of cell differentiation after the stage in 

 which it is here described. 



The great majority of the pollen grains present no external markings ; but 

 every here and there, in addition to merely accidental breaks in the extine, mark- 

 ings may be observed which appear to represent cell walls, rather than to be entirely 

 due to chance. A series of grains presenting such markings is arranged arbitrarily 

 in figure 84 so as to pass from the simpler forms to the more complex. The 

 most frequent form of marked grain has a circle or a slight circular pitting at 



