36 STRUCTURE AND LIFE-HISTORY OF HAY-SCENTED FERN. 



planes at right angles to one another, and at last irregtilarly (fig. 230), to 

 produce 32 sperm mother-cells. These separate and round off, and in 

 each one a spiral spermatozoid develops. As the central mass enlarges it 

 pushes itself down into the center of the stalk-cell until it reaches the 

 original basal wall (figs. 230, 237). Thus the stalk-cell becomes ring- 

 shaped, though at first it was a disk (figs. 226, 229). At maturity the 

 contents of the antheridium swell up by absorption of water, the cap-cell 

 is ruptured irregularly, and the sperm mother-cells escape. After 45 to 

 50 seconds the mother-cell wall bursts and the spermatozoid swims rapidly 

 away with a steady rotary motion, bearing a granular vesicle at the pos- 

 terior end. From cultures of male prothallia kept free from surface-water 

 it is easy to get numbers of spermatozoids by mounting the prothallia in 

 water. Mr. W. D. Hoyt found them to be distinctly attracted by a malic- 

 acid solution of suitable strength. The body of the sperm makes about 

 two and a half coils. The anterior end is more slender and more closely 

 coiled. 



TABLE 7. Development of antheridium. 



<Pro.thallial cell 

 .Stalk cell 

 Antheridial cell( /dome-like ^walfcell 



Body cefl{ outer cell )^ cover cell 



inner cell 32 sperm mother cells 



Female prothallia are always cordate in shape and bear their archegonia 

 on the under side of a central thickening or cushion. They begin to form 

 sexual organs when still narrower than long, five or six weeks from sow- 

 ing of spores. If not fecundated they continue to grow larger and broader, 

 and produce many archegonia in succession over all the central lower sur- 

 face. The upper surface is at first flat, but in old females the margins 

 may become reflexed dorsally, and the plant forms a broad, erect funnel, 

 open on one side. The largest in my cultures are 5 to 7 mm. tall and 6 

 to 9 mm. across. I found one out of doors 7 mm. wide and 4 mm. long. 



The archegonium develops from a cubical superficial cell of the pro- 

 thallus, near to the initial cells. This cell may be a semi-segment, involv- 

 ing half the thickness of the prothallus (fig. 202), or it may be simply 

 the outer part of a semi-segment (figs. 206, 214), according to its point of 

 origin on the prothallus and the size and thickness of the latter. In any 

 case the definitive archegonial mother-cell first cuts off a thin superficial 

 cell, the neck rudiment (fig. 202). Then on the opposite side a similar 

 basal cell is separated, leaving a large central cell (figs. 206, 207). The 

 basal cell divides crosswise into four and forms the innermost part of the 

 wall of the archegonium (fig. 208). The neck rudiment similarly divides 

 crosswise into four (fig. 207). Its first cleavage wall is parallel to the 

 longitudinal axis of the prothallus. Now the central cell enlarges and 

 pushes out the four neck-rudiments. As the latter project more and more 



