392 STUDIES IN FOSSIL BOTANY 



entered, and there terminated (see Fig. 149, A). The 

 canopy may represent a provision for water-storage, 

 serving, perhaps, as has been suggested, to supply the 

 necessary liquid for pollination by means of a " drop- 

 mechanism." The outer layer of the integument has 

 a columnar or palisade-like structure ; there is some 

 evidence that a secretion of mucilage took place from 

 this layer, as in the testa of so many recent seeds. 



As in the recent Cycads and in Ginkgo, the free 

 apex of the nucellus forms the pollen-chamber, a cavity 

 for the reception of the pollen-grains, 1 which in the case 

 of Lagenostoma has a peculiar and characteristic form, 

 for a solid column of tissue rises up in the middle of the 

 chamber, leaving only a narrow annular space, in which 

 the pollen-grains are found (Figs. 143, 147, 148, 149, 

 A). The outer wall of the flask-shaped pollen-chamber 

 projects a little through the micropyle, as an open tube, 

 and no doubt received the pollen-grains directly, without 

 their having first to traverse a micropylar passage 

 (Figs. 147 and 148). The pollen-grains occurring in 

 the chamber appear to have been multicellular, but 

 this point is better shown in other cases (see Figs. 173 

 and 174, PP- 45 8 and 459). 



The interior of the seed has not been found in a 

 good state of preservation. The outlines of the mega- 

 spore or embryo -sac can usually be traced, but its 

 membrane cannot always be distinguished from the 

 disorganised tapetal layer of the nucellus. 



The discovery of the seed of Lyginodendron afforded, 

 for the first time, the proof that a member of the 

 Cycadofilices was a seed-bearing plant, and led, as 



1 For the pollen-chambers see Chap. XII. p. 542. 



