330 Howe: Observations on the 



hypopeltal processes, polytomous disc- filaments, etc.) evidently is 

 not a complicated aggregation of whorls of primary branches and 

 the sporangia are, ivith little doubt, not to be compared with the ordi- 

 nary verticillate branches or branchlets. As Solms-Laubach has 

 maintained, the sporangia in the Acetabuleae are most naturally to 

 be compared with those of Bometella, in which genus the sporan- 

 gia arise laterally and irregularly from the primary whorled 

 branches (*. e. y from the branches of the " first generation M ) and 

 have no evident homologies with the verticillate sterile branches. 

 It may be remarked that, according to Cramer, the sporangia in 

 Borne tell a nitida (Harv.) Mun.-Chal. occur singly on the branches 

 of the first order, while in B. capitata (Harv.) J. G. Ag., they are 

 more numerous, ranging from 9 to 35 for a single branch. Now 

 in view of the fact that in the Acetabuleae (if our observations on 

 Aciadaria Schenckii and Acetabidiim crenulatum * may be consid- . 

 ered typical for the group) the hypopeltal process and the distal 

 portion of the coronal process are lateral outgrowths like the 

 sporangium, we are of the opinion that these structures are best 

 looked upon as abortive sporangia. The logical result of this com- 

 parison of the ontogeny of the ray with the relation of parts in 

 Bornetella is the conclusion that the whole cap, with all its radially 

 arranged parts except the vestibules, corresponds to a single primary 

 whorl of branches. The original outgrowth which gives rise to the 

 terminal rudiments and to the lateral sporangia is the branch of 

 the first order {i. e. % corresponds to the first segment of the ordinary 

 primary branch), whence it follows that the sterile polytomous fila- 

 ments which may arise from it later are branches of the second 

 order. The velum partiale, as it might be called, which separates 

 the base of the ray (the chamber of Cramer's " Zwischenstiick ") 

 from the vestibule (Figs. 33 and 34) is evidently homologous with 

 the constriction which separates the base of the primary sterile 

 branch from the main axis of the plant It is here that the ray 

 detaches itself when the cap finally falls — though the fertile spor- 

 angia alone are often first detached. In this connection, it is of 

 interest to note that the primary sterile branches show at their be- 

 ginning distinctly recognizable basal cushions corresponding to 



♦Seepage 331. 



