8 Watson, TJic Cone of BotJirodendron mundiivi. 



its lower part (See Fig. 2 of Plate). The lamina continues 

 at least to the height of the top of the sporangium, but I 

 could form no satisfactory idea of its structure in this part 

 from existing sections. 



Spores. 



Each cone carries both micro- and megaspores, and it 

 seems most likely that the microspores were in the upper- 

 most sporangia, the megaspores below, as is the case in 

 Williamson's longitudinal section. In this connection it 

 should be mentioned that the microsporangia are usually 

 smaller than the megasporangia. The microspores have 

 the form of quarter spheres and are about '027 mm. in 

 diameter. 



They are often found associated in tetrads, and 

 except for the ridges produced by this association are 

 without ornament. 



The megaspores were several times described by 

 Williamson (Will. '78). They are of roughly spheroidal 

 form, and are provided with a projection which interlocks 

 with those of the other spores of the tetrad. Encircling 

 the equator of the spore, assuming the projection to be 

 the pole, is a belt of ramified hairs about 0-15 mm. long. 

 These are exceedingly characteristic, and render the 

 identification of the megaspores easy. No more than 

 four megaspores have been found in any sporangium, and 

 it is almost certain that only one tetrad is normally 

 developed in each sporangium (See Fig. 4 of Plate and 

 Text-fig. 2). 



For further illustrations of the megaspores see 

 Williamson '78, pi. 23, figs. 58, 59, 60, 64, 66, and "8o,pl. 15, 

 fig- 9- 



