81 



but did not follow the development. This brief study of the 

 reproductive organs showed that the species differed a good deal 

 from those described by Rauwenhoef, especially in the structure 

 of the antheridium, and it therefore seemed desirable that a 

 further study of the genus should be made. During a recent 

 visit to South Africa and to the East Indies I therefore made 

 an effort to secure prothallia of as many species of Gleichenia 

 as could be obtained for comparison with the specimens of 

 G. pectinata collected in Jamaica some years ago. 



Rauwenhoff's account of the germiuation of the spores and 

 the early development of the gametophyte is very satisfactory, 

 and as the growth of the prothallium is rather slow, no attempt 

 was made to repeat his exjDeriments, and the following account 

 is based entirely upon prothallia found growing in their natural 

 habitat. 



Most species of Gleichenia grow in dense masses, and where 

 they occur upon banks or overhanging ledges of rocks it is 

 not uncommon to find prothallia in considerable numbers in 

 crevices, or upon the earth beneath the overhanging masses of 

 plants. According to Rauwenhoff's account the spores are always 

 destitute of chlorophyll and the germination is rather slow. In 

 some cases he obtained the first signs of germination in ten 

 days, but in most cases the period of germination was fi'om 

 two to three weeks. The development of the prothallium 

 according to Rauwenhoff's account more nearly resembles that 

 of Osmunda than any other ferns that have been studied, and 

 Gleichenia shows a number of other points in which it resem- 

 bles Osmunda. A good deal of variation is shown in the early 

 stages of germination, l)ut in typical cases the young prothal- 

 lium soon assumes the familiar heart-shape and becomes some- 

 what elongated. A midrib develops very early as in Os/tiimda, 

 and as we shall see, this midrib becomes extremely conspicuous 

 in the older prothallium of some species. This conspicuous 

 midrib usually enables one to distinguish between the prothallia 

 of Gleichenia and those of other ferns which may he growing 



with them, l)ut this is not always the case, and it is some- 

 Ann. Jaid. bot. Buitenz. 2e Ser. Vol. \U. 6 



