﻿EISPORANGIATE AXES. 



159 



the synangium are : First, the outer palisaded wall-tissue ; second, the delicate 

 parenchyma layer, or chief ground tissue ; third, the sporaugial loculi containing 

 much well-preserved pollen, but usually delimited only by desiccated pollen grains, 

 or collapsed remains of wall cells; and, fourth, the thin, elongate-celled layer bound- 

 ing the sulcus between the two rows of sporangia; dehiscence of the synangium 

 taking place early along the median apical line, and of the sporangium longitudi- 

 nally along the inner median Hue as in Marattia. (Cf. figures 81 and 82 ; also 

 plate xxxvu). 



Regarding the character of the tissue bounding the sporaugial loculi, a word 

 yet remains to be said. The cells forming the yellowish-brown iron-stained band 

 mentioned above as marking the locular walls are so uniformly collapsed that it is 

 difficult to determine whether they are wholly septal or in part tapetal. It would 



7 8 9 10 11 12 13 



Fig. 83. — Pollen grains of existing and fossil Cycads. 



Nos. 1-6. — Ceratozamia longifolia Miquel. ■ 500. No. I, mature pollen in dry condition; Nos, 2, 3, the same swollen in 

 water ; Nos. 4-6, the respective transverse sections or end views. After Juranyi (70). 



No. 7. — Stephanospermum, showing supposed traces of internal structure. '■ 100. From Renault (I 17). 



Nos. 8-1 I . — Cycadeoidea etrusca. Somewhat desiccated pollen from a bisporangiate strobilus, as figured by Capellini and Solms. 



Nos. 12-19. — Cycadeoidea dacotensis. A series of pollen grains, including both collapsed and distended forms, selected from 

 various sections cut from Fruit No. I, T. 214. ;■ about 350. Observe that grains 17-19 are intermediate in size between 

 grains 3 and 7, in accordance with hypothetical reduction stages of the prothallium in geological time. 



appear, however, that the sporaugial wall was two cells in thickness rather than 

 one, in this respect approachiug the crushed double layer of wall cells observed by 

 Lang (75) in St anger ia paradoxal 



Pollen grains. — One of the most striking features of the silicified strobili of 

 Cycadeoidea dacotensis is the presence of numerous pollen grains outlined in great 

 perfection. As already stated, cycadeoidean pollen was first observed in the fructi- 

 fication of Cycadeoidea etrusca by Count Solms, and figured by him (22). In this 



*If by any chance the colored band represents a long persistent, but finally crushed tapetum, the 

 condition represented would be quite identical, layer by layer of cells (in the transverse longitudinal section 

 only), with that seen in a similar section of a nearly mature sporangium of Angiofteris evecta given by 

 Campbell (20, fig. 143). The greatest difference would lie, of course, in the absence of a rudimentary 

 annulus and the strong development in the present forms of the outer prismatic layer with its projection 

 as two valves beyond the sporangia to meet lip-like in the line of dehiscence. But it would appear from 

 the investigations of Bower (9) that the condition figured by Campbell is not the usual one observed in 

 ingio$teris. If, however, it should approximate the condition seen in these fossil forms, we would 

 then have indicated in them imperfect septation of the loculi carried to a high degree, an anomalous con- 

 dition frequently noted by Bower (9) in both Marattia and Dancea. 



