PTERIDOPHYTES— FILICALES 



319 



sporangia, the division of the spore mother-cells, and even during the 

 earlier stages in the formation of spores. Except in the case of the 

 youngest sporocarps, it is better to cut off a small portion at the top 

 and at the bottom to facilitate fixing and infiltration. The mother-cell 

 stage and the young spores will be found in sporocarps which are just 

 beginning to turn brown. In nature, no further nuclear divisions take 

 place within the sporangi- 

 um until the next spring, 

 but the wall of the sporo- 

 carp becomes extremely 

 hard. Sporocarps for 

 germinating should not 

 be collected until they 

 are so hard that it is im- 

 possible to crush them 

 between the thumb and 

 finger. They can be kept 

 in a box until needed for 

 use. When you find them 

 in good condition, make 

 a big collection, for they 

 retain their power of 

 germination almost in- 

 definitely, sporocarps from poisoned herbarium specimens 50 years 

 old germinating readily. Sporocarps which have been kept in 95 per 

 cent alcohol for years germinate almost as quickly as those which have 

 been kept in a dry box. 



To germinate sporocarps, cut away a portion of the hard wall along 

 the front edge and place the sporocarp in a dish of water. The gelati- 

 nous ring with its sori will sometimes come out in a few minutes. In 

 less than 24 hours, sometimes within 10 or 12 hours, microspores, 

 starting from the one-cell stage, will produce the mature sperms; and 

 the development of the female gametophyte is equally rapid. Starting 

 with the uninucleate megaspore, the stage found when the gelatinous 

 ring comes out, the archegonium may be developed and fertilization 

 may occur within 12 hours; and within 36 hours, stages hke that shown 

 in Figure 109 may be reached. At the end of a week, there may be 

 green sporophytes more than a centimeter in length. 



It is obvious that material should be fixed at frequent intervals li 



Fig. 109. — Marsilia quadrifolia: upper portion of me- 

 gaspore with an archegonium containing a young embryo. 



X212. 



