182 DopGEeE: RELATIONSHIPS OF FLORIDEAE AND ASCOMYCETES 
justification. Even though the ascogonium be completely en- 
closed at first, if the hymenial layer subsequently develops super- 
ficially the ascocarp must certainly be described as discocarpous 
and not properly cleistocarpous at any stage. Illustrations of 
permanent cleistocarps are the well known types Sphaerotheca, 
Chaetomium fimeti, Aspergillus, Elaphomyces, etc. ‘Illustrations 
of those that are gymnocarpous and then become closed are Tuber 
excavatum, Balsamia (Fic. 8, D), Choiromyces, and Hydnocystis. 
Two types of cleistocarps have been distinguished. We may 
take the mildews as well known cases of the first type whose 
- method of development has been fairly clear since De Bary’s time. 
The sporophyte proper which develops from the fertilized egg 
remains enclosed in a gametophytic envelope, the perithecium 
(Fic. 8, A), which finally bursts irregularly when the spores are 
ready to germinate. Thesecond type of cleistocarp, which is open 
at first but later becomes closed by the growth of the peridium 
(Fic. 8, D), has been carefully investigated by Fischer (42) and 
Bucholtz (22-24). In a number of the Tuberineae at the time. 
when the hymenium is first recognizable as such it is freely 
exposed to the exterior. Later by a process of infolding and the 
active growth of a peridium it becomes entirely enclosed. Buch- 
oltz (23) believes that the mature form of the fruit body, for 
example, whether it is angiocarpous or gymnocarpous, is in a great 
measure determined by the environment and is not a basis for 
determining phylogeny. Bucholtz calls this second type of cleisto- 
carp ‘“‘pseudoangiocarp” and proposes to use the term ‘“‘ hemi- 
angiocarp ”’ to distinguish the abnormal forms of Tuber puberulum 
where in rare cases the young hymenium is entirely covered at 
first by a very delicate weft of hyphae which extends out from the 
peridium proper. He agrees with Dittrich and Durand that any 
Discomycete in which the ascogonium is enveloped by sterile 
hyphae is in its ontogeny in fact cleistocarpous, yet in his treat- 
ment of the Tuberineae he entirely ignores the possibility that 
ascogonia may yet be found in them which are surrounded at an 
early stage by a layer of enveloping hyphae, and classes such 
forms as Tuber excavatum as gymnocarpous, or pseudoangio- 
carpous, as he prefers to call them. As I have noted it is of little 
importance whether or not the ascogonium is enveloped in its 
