26 DOUGLAS HOUGHTON CAMPBELL ON THE 



out. The neck-cells of the same archcgonium, examined twent3'-four hours later, showed 

 a decided broAvn color, which was not observed in unirapregnated ai-chegonia of the 

 same age, and the germ-cell had divided (PI. 5, fig. 10). 



In making experiments in fertilization, a number of male prothallia, freed from earth, 

 were placed upon a slide, and with them longitudinal sections of female prothallia, some 

 of which are almost certain to contain ripe archegonia. If the prothallia have Ijcen kept 

 someAvhat dry for two or three days, especially in warm weather, both archegonia and 

 antlieridia will open very soon after they are ])laced in water. In this way freshly 

 opened archegonia and nimierous antherozoids were present upon the slide, and could 

 easily be observed, but although many trials Avei'e made, the antherozoids in the great 

 majority of cases fiiiled to enter the archegonium at all. 



The prothallia are always strongly dioecious, the male prothallia never bearing arche- 

 gonia, and the female only in rare cases developing antheridia, and then only in small 

 numbers, and before the archegonia are mature. 



Various experiments were made to find out what were the most favorable conditions 

 for growing the spores, and several were more or less successful. The eai'liest stages 

 can best be observed by placing the spores simply in water, as they are then free from 

 foreign matter; but they do not develop in a healthy manner if left in water, the pro- 

 thallium becoming very long and slender, the transverse septa being wanting, or only 

 developed at long intervals. Finding that some fern prothallia g^•e^y naturally on rotten 

 wood, spores that had germinated in water Avere transferred to this material and devel- 

 oped male prothallia, but no female ones. Probably further trials might have been more 

 successful. The best results Avere obtained by soAving the spores in fine earth in shal- 

 loAv earthen saucers Avhich Avei-e kept under glass to prevent too rapid evaporation. In 

 cold weather, they Avere exposed to direct sunlight, but in warm weather were kept pai'- 

 tially shaded. Care must be taken not to keep them too Avet, for if they are kept soak- 

 ing wet for a few days they are apt to decay, besides inducing a groAvth of algae, such 

 as Oscillaria, etc., Avhich sometimes interfere Avith the groAvth. In cultures that have 

 been kept for some months, it is almost impossible to prevent the groAvth of mosses, 

 Avhose protonema, unless kept down, sometimes interferes Avith the ferns; but if the pro- 

 thallia are Avell established, a little care in removing the mosses from time to time Avill be 

 sufficient. SeA'^ere freezing failed to kill the prothallia, provided care Avas taken to thaw 

 them out gradually. 



Attempts to groAV the prothallia in porous pottery met with indifferent success. 



All of the prothallia, from which the foregoing observations Avere made, Avere groAvn 

 artificially, none having been met with growing naturally. 



Section III. The Embryo. 



The first division of the germ-cell is completed within tAventy-four hours after fertil- 

 ization and is effected by a wall (the basal Avail) Avhich is slightly inclined to the surface 

 of the prothallium and perpendicular to its longer axis. The basal Avail ma^'be inclined 

 either toAvard the front or back of the prothallium and divides the embryo into tAA^o cells, 

 the epibasal lying in front, and the hypobasal behind (PL 5, fig. 15). Each of these 

 cells is next divided by a wall (the transverse Avall) perpendicular to the basal wall and 



