LABOULBENIALES 381 



When no longitudinal division occurs, a biseriate axis results, as in R. 

 biseriata (Fig. 257, 4) and R. dichotoma (Fig. 255, 4). These biseriate 

 forms may be regarded as more primitive, since in cases of injury or peri- 

 thecial abortion, secondary axes which develop from them adventitiously 

 and might be expected to show an atavistic tendency, are biseriate. 

 Occasionally apparently normal individuals of the biseriate type may 

 develop in species which are ordinarily triseriate. 



At a definite stage of development, a longitudinal division occurs in 

 the terminal cell of the anterior series. Of the two resulting cells, the 

 inner becomes the primordium of the perithecium while the other either 

 ceases its activity and subtends the perithecium, as in R. rostellata (Fig. 

 256, 7 and 8), or continues to divide transversely until it reaches the apex 

 of the developing perithecium, as in R. circumdata (Fig. 256, 1 and 2). 

 Similarly, the posterior series may end below the base of the primary 

 appendage which at maturity may be subtended by the posterior terminal 

 cell as in R. coptengalis (Fig. 256, 9), or it may push aside the primary 

 appendage and continue along the edge of the perithecium, as in R. 

 biseriata (Fig. 256, 4 and 7). Such a case illustrates the combination of 

 trichothallic and apical growth, in which growth is trichothallic below the 

 primary appendage and apical beyond it. 



The cells of the outer series may cut off one or two smaller cells, by 

 single or successive separation downward from their upper, outer angle, 

 which organize either single secondary appendages or antheridia. The 

 relative position of the appendiculate cells may not always be the same, 

 even in the same individual; they may be vertically superposed, horizon- 

 tally seriate or separated from the mother cell in such a way that they 

 lie crowded in different radii of the same circumference. A slight pro- 

 trusion is abjointed and develops a simple unicellular appendage, while 

 the septum becomes variously blackened and constricted. 



The antheridium begins to develop exactly as an appendage. The 

 septum occasionally remains unmodified and the antheridium immersed. 

 The primary division of the original appendiculate cell separates an inner 

 stalk cell from an outer which organizes the venter and neck of the 

 antheridium. In the venter a small basal cell may be seen, above which 

 a group of two or more antheridial cells discharge spermatia through 

 minute pores into the main cavity of the neck. These are evanescent, 

 the whole content of the antheridium disorganizes, leaving a contin- 

 uous cavity which might be mistaken for the simple cavity of the 

 Laboulbeniaceae. 



In R. macrandra (Fig. 254, 6), besides the free antheridia of the normal 

 type, giant antheridia (Fig. 254, 4 and 5) are produced in which numerous 

 elongate antheridial cells arise directly from a hemispherical basal cell of 

 the venter, arranged in a subterminal whorl. In this type the sperms are 

 discharged in great numbers and pass through short pores into a chamber 



