Phyllidium

The five species described above form an interesting series illustrating the gradual modification of the entire phyllidium into a sucker, just as individual loculi become modified into suckers.

The excretory vessels form a hairpin loop just inside the phyllidium (Pl. 5 Fg.1). It seems strange that the excretory vessels do not extend to the margins of these giant phyllidia since they invariably do in other forms with large phyllidia such as Phyllobothrium lactuca, etc.

The four phyllidia are arranged in pairs with each phyllidium occupying a corner of the rectangular scolex.

The lateral lobes of each opposite phyllidium being thus brought together and forming an apparent whole, botanists supposed they had before them two stigmata in this order opposed to the placentae, which was contrary to all analogy.

The forward margin of each dorsolateral phyllidium overlaps the rear margin of the adjacent phyllidium. This arrangement tends to channel drainage water toward the ventral surface of the gametophyte, where some of it is retained in tiny pockets that are bounded on the lower side by the ventral lobes of the dorsolateral phyllidia.

Interference-contrast micrograph through the abaxial surface of a proximal cell of a phyllidium of Tortula ruralis ten minutes after rehydration from the desiccated state.