A^^^ A NEW GROUP OF FLOWERING PLANTS. 133 



usually on the back of the fertile leaves, produce on germination not 

 a new fern-plant, but a small green expansion showing no dif- 

 ferentiation into stem and leaf, and attached to the soil only by a 

 few colourless root-hairs. From this expansion, the pyothallium, arises 

 a new fern-plant similar to the original spore-producing individual. 

 This new plant is the result of a sexual process. On the under surface 

 of the prothallium are two sets of organs, the male, or anthevidia, 

 containing the male cells or antheyozooids, and the avchegonia, or female 

 organs, containing the female cell or oospheve. The antheridium con- 

 sists merely of a wall of a single layer of cells enclosing the naked 

 unicellular spirally-coiled antherozooids. The archegonium consists 

 of four rows of cells forming a projecting neck, round a row of 

 canal-cells terminating at the central cell or oospheve. Fertilisation 

 takes place by the rupture of the wall of the antheridium, and the 

 escape of the antherozooids which swim about in the water present 

 and are attracted to the archegonium by a mucilaginous secretion 

 resulting from the disorganisation of the canal-cells. They pass 

 down the passage thus formed and penetrate the naked oosphere, 

 which is at once invested with a cell-wall and becomes the oospore. 

 On germination, the oospore produces the young fern-plant. 

 We may represent the life history in a tabular form : — 



In this case the sexual generation represented in the prothallium 

 is quite distinct from the previous asexual generation or fern-plant, 

 and also gets quite free from the spore. 



The spores are contained in small roundish capsules, the 

 sporangia — there are usually sixteen in each — arising from the 

 division of a single central cell, the archespoyinm. They are set free 

 by the bursting of the sporangium-wall. The true Ferns are homo- 

 spoyous, i.e., produce only one kind of asexual spore, and one prothallium 

 bears both antheridia and archegonia, but the nearly allied Rhizocarps, 

 which include Salvinia and Pilulayia (the Pillwort, a local British plant), 

 are Jieterospovons. Two sorts of spores are produced in two sets of 

 sporangia. The smaller micyospoyangitim produces a number of small 

 spores, micyospoves, and the larger macrospoyangium one large macvospove. 

 The indication of sex has been carried back into the asexual 

 generation as far as the sporangia, but both kinds of sporangia are 



