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1906] OVERTON—THECOTHEUS PELLETIERI 455 
of the oogonium divides by successive division until eight free auclei 
are formed. Cross walls are then formed in such a manner that 
one cell contains two nuclei. This cell is larger and finally develops a 
single ascus, as in Sphaerotheca. No reduced sexual fusion, such as 
described by BLACKMAN and FRASER, was observed, and RAMLOw 
-believes that Thelebolus is strictly apogamous. Although this form 
has been placed among the Hemiasci by several earlier authors, 
Ramtow from his studies believes it to be a member of the Ascobo- 
laceae, as suggested by SCHROETER and REHM. 
That a sexual reproduction occurs in the lichens, comparable to 
that found in the red algae, as first described by Stant (77), and 
confirmed by Borzr (78) for other species of Collemaceae, has been 
practically established by the investigations of several later authors. 
Although Krappe’s work (’83, ’91) on Cladonia, Baeomyces, and 
Sphyridium would indicate that sexual organs were absent in these 
forms, yet WAINIO (’90, 97, ’98) claims to have found trichogynes in 
very young podetia of Cladonia, which would show that sexual organs 
are present. Baur’s work (’98) on C. crispum confirms STAHL’s 
observations in every detail. He figures and describes carpogonia 
and trichogynes. His work also shows that fertilization is a necessity 
to the development of asci. If the carpogonia are not fertilized by 
a spermatium, they develop vegetative hyphae; while each cell of 
the carpogonium which has been fertilized develops ascogenous 
hyphae. The discovery by STAHL and Lrypau (’88) of trichogynes in 
Physcia pulverulenta has been confirmed by DARBISHIRE (’99), who 
finds a trichogyne and a carpogonium, each cell of which is uninu- 
Cleate. The cells of this carpogonium become connected so as to 
form a more or less continuous structure. LrypAU (788, ’89) has 
also described the presence of trichogynes in several other species 
of lichens, but denies that they are sexual organs. In a more recent 
work Baur (:o1) finds that Parmelia acetabulum, Anaptychia ciliaris, 
Pertusaria communis, and Pyrenula nidia have carpogonia. Anap- 
tychia possesses a single carpogonium, while the other forms have the 
Carpogonia in groups, thus making the fruit body a compound apo- 
thecium. Baur’s opinion is that fertilization occurs by means of 
Spermatia combining with the trichogynes. In a still more recent 
Work Baur (:04) finds the ascogenous hyphae of Parmelia, Anapty- 
