XI THE HOAIOSPOROUS LEPTOSPORANGIAT.-E 363 



special gcmm?e developed in many of them, often in L^rcat 

 numbers. In an undetermined species of Hymenophylluni col- 

 lected in the Hawaiian Islands (Fig. 188) these gemmae 

 occurred very abundantly upon prothallia that had ceased to 

 form sexual organs. Here a marginal cell grew out and curved 

 upward, and the tip was cut off by a transverse wall from the 

 basal cell. In the terminal cell are next formed a series of 

 vertical walls, which transforms it into a row of cells extended 

 at right angles to the axis of the pedicel. One of the central 

 cells now bulges out laterally, and this papilla is cut off by 

 an oblique wall and forms the beginning of a short lateral 

 branch, so that the fully- developed bud has somewhat the 

 form of a three-rayed star, and in this condition becomes 

 detached and grows into a new prothallium. The prothallia 

 formed in this way often do not develop a flat thallus, but may 

 remain filamentous, and each ray may produce antheridia either 

 terminally or laterally (Fig. 187, C). In case a flat thallus is 

 formed, only one or sometimes two of the rays grow out in this 

 form, the other having only a limited growth, and terminating 

 in a short rhizoid. In short, the process is very similar to 

 that in the germinating spores. 



TJie Sexual Organs 



Bower ^ has investigated the structure of the antheridium 

 in Tridiomanes, and Goebel " both Trichonianes and Hymeno- 

 pJiyllum. My own study of their development has been 

 confined to an undetermined species of HyvienopJiylluni from 

 the Hawaiian Islands, but the results of my observations agree 

 entirely with those of other observers. The antheridia arise 

 mainly upon the margin of the prothallium, or upon the ends 

 of the filamentous ones. After the mother cell is cut off, there 

 is usually formed another transverse wall, by which a short 

 pedicel is produced. A funnel-shaped wall does not ever seem 

 to be formed, but the next division walls are more like those 

 in Osimcnda, and extend only part way round the circumference 

 of the mother cell. After a varying number of basal cells are 

 thus formed, a dome-shaped wall arises, separating the central 



^ Bower (8). 



- Goebel, Ueber epiphytische Fame und Muscineen. Ann. du Jardin hotanique 

 de Bintenzo?'g, vol. vii. 



