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



of the sporangium nearly touches the stalk. Meanwhile some spores have 

 fallen out, others remain in each half of the sporangium. Then suddenly 

 the annulus springs back to its former place, throwing its load of spores 

 several centimeters. Straightway it begins slowly to bend back again, 

 and repeats the operation. The springing of the thin walls during both 

 the extension and the recoil of the annulus throws out several spores. 



GAMETOPHYTE. 



Spores sown on moist micaceous earth about Octobers, 1905, had mostly 

 germinated and formed protonemata by the 25th.* About October 1, 

 1905, also, fresh male and female prothallia and young plants in various 

 stages of development were found in a ravine near Baltimore, Maryland. 

 In germination the spore-coat bursts at the tetrahedral angle. The intine 

 bulges out, and a cell with many chloroplasts appears (fig. 177). It imme- 

 diately sends out a rhizoid which is separated by a wall from the cell. 

 Some of my cultures became temporarily dry at this stag'e, and the first 

 rhizoid died. Another was soon sent out from a point farther up on the 

 same cell (figs .191,193). The protonemata assumed a great variety of shapes 

 (figs. 178-199). There were from one to six cells, in linear series. The 

 basal cell was sometimes very long and slender (figs. 184, 196), or rarely 

 broader than long (fig. 182). The basal cell was usually the longest of all, 

 but not always (fig. 197). The growth of the protonema is by transverse 

 divisions in the apical cell. Rarely an intercalary division occurs in a 

 longitudinal plane. 



Sooner or later the terminal cell divides longitudinally in half (fig. 189). 

 One half enlarges more than the other, causing the partition to become 

 oblique. Then an oblique wall cuts the larger cell, striking the next 

 earlier wall nearly at right angles (figs. 185, 196). The result is a two- 

 sided apical cell, which continues to divide parallel to its two sides for a long 

 time (figs. 187, 188, 190). The young gametophyte now becomes broader 

 at the apex (figs. 194, 195). Soon the cells on either side of the initial 

 outgrow those just behind it, and the prothallus assumes its cordate shape 

 (figs. 199, 200). The initial is then changed by a transverse wall across 

 its posterior end (fig. 203). After this it divides into two longitudinally, 

 and we can henceforth recognize only a group of marginal initials (fig. 

 200). Each of these cells divides on three sides, viz, two lateral and one 

 posterior (figs. 202, 204-207, 214). 



*My cultures were sown in 3-inch to 6-inch flower-pots and pans on micaceous soil 

 dug from deep down in a newly exposed bank of earth. Ripe leaves were laid on the 

 pots, covered loosely with papers, and allowed to dry and shed their spores. Or, the 

 de'bris of dried fertile leaves was sown. The pots and pans were never sprinkled, but 

 were kept standing in i to 2 cm. of water, covered with glass plates, before a west 

 window of the Johns Hopkins Biological Laboratory. 



