FERTILIZATION ASD FRUIT-FORMATION IK CRVPTOGAMS. 65 



The aniheiidia aiise in tiie same maimer as the froiii-raduuents. A superficial 

 cell of the thallus is enlai-ged into a papilla, and, by the i-epeated partition in all 

 directions of its first segments, a body of tissue is produced, which includes a delicate 

 stalk and a thickened uppex portion, either davate or spherical in shapa The 

 latter part consists of a multicellular sac-like envelope and a parenchymatous 

 filling-tdssue indexed within the envelope. In each cell of the internal tissue the 

 protoplasm Bsishions itself into a spiisUy-bent spermatoaoid, and shortly afterwards 

 the entire fiUing^in tissue is resolved into its separate cells. The antheridium now 

 opens at the top, and the loose cells with the mucilage in which they are embedded 

 are ejected into tiie surrounding aqueous medium composed of rain or dew-di'ops. 

 The spermatoKoids then escape from their delicate cell-membranes, and SAvim about 

 tiie water by the help of the two long cilia wherewith each is furnished (see voL i. 

 p. 29, figs. 7 ' and 7 ^•)k Ps^ssing down tiie open neck of the amphigonium, now 

 filled with mudlage only, they succeed in reaching the oogonium in the enlarged 

 base of the froit-rudiment and apply themselves closely to its sur&ice; a constitueni 

 portion of the spermatoplasm is absorbed into the ooplasm with the result that the 

 latter becomes fertilized. 



TTsuaIfy several »atheridia are situated dose together. In Mosses they are 

 mingled with paraphyses, structures resembling hairs, the ^gnificanee of which 

 has not yet been explained. In many spedes one individual devdops only anther- 

 idia, another only amphigooia; but in other spedes antheridia and amphigonia. 

 are developed side by side on the same Moss-plant. Where the latter is the case 

 dther the oogonium exhibits an earlier devdopment than the antheridium, or the 

 reverse is the case. Either the passage leading to the oogonium throu^ the neck 

 of the amphigtminm is opened whilst the adjacent antiieridia are still dosed, or 

 dse the spermatonads are set &ee from the antheridia at a time when access to 

 the oogonium is still barred by the lid-cells of tite amphigoninm. As in so mamy 

 cases of a similar kind this contrivance prevents a union between the o<^asm and 

 the spermatoplasm prixluced by the same individual, and &,vours cross-fertilization 

 between difi^rent individuals. 



In scone Liverworts the antiieridia and amphigonia are surrounded by annular 

 walls, and these organs thea appear to be sunk in depressions of the thallus. In 

 other liverworte separate lobes or branchlets of the thallus are transformed into 

 stalked shidds or discs, and the antiieridia and amphigonia are farmed in spedat 

 niches and ccanpartments on the surface of the shidds. Those Musdnese which 

 have their thaUi difierentiated each into a cauline axis and cellular laminse 

 resembling leafiets, devdop antiieridia in the axils of the leaflets, or else in jntcher- 

 8hsq>ed cavities at the tops of tiie stems. In Mosses tiie prindpal or secondary 

 axes terminate in groups of antheridia or amphigtmia^ and specialiaed leaflets act 

 as ^ivdopes or roofe and constitute the "peiich^tium" Sometimes these leaflets 

 have the appearance of floral leaves, as, for instance, in the Hair-Mosses {PoUf- 

 tndtwnii, one spedes of wMch is represented in Plate IX. in tiie foreground to the 

 left "Die antheridia smd amphigonia are here distiibuted on different individuals. 



V<».II. 55 



