ORDER HYPOCREALES 285 



temperate Eurasia. The elongated black stromata resemble unopened 

 rust sori. 



Order Pyrenulales. The perithecial lichens make up a group of about 

 15 families, over 80 genera, and more than 2000 species. They form typical 

 lichen thalli in combination with various algal hosts. Most of the species 

 are crustose or foliose, in only two genera fruticose. The order does not 

 seem to form a compact monophyletic group but its various families seem 

 rather to show relationship to different families of the Sphaeriales and 

 perhaps to some of the Pseudosphaeriales. The perithecia may be sunk 

 singly in the thallus or may be produced in a stroma strongly resembling 

 that of Diatrype. Among the common genera may be mentioned Ver- 

 rucaria, with nearly 300 species forming crustose growths on rocks into 

 which the hyphae may penetrate to a considerable distance. The peri- 

 thecia are black and sunken in the thallus. The eight ascospores are one- 

 celled, ellipsoidal, and hyaline or brown. The algal host is Protococcus or 

 Palmella. Pyrenula includes about 175 species usually on bark, growing 

 on the alga Trentepohlia. The perithecia resemble those of Verrucaria, 

 but the ascospores are several-celled. Long slender conidia are produced 

 in pycnidia. Trypethelium consists of about 75 bark-inhabiting species, 

 mostly tropical and subtropical, whose perithecia are produced in a 

 cushion-like stroma. The 37 or more species of Astrothelium are also 

 tropical or subtropical, on bark. Their perithecia are arranged radially 

 ill the stroma with their long necks approximated or joining into a com- 

 mon ostiole. Practically nothing is known as to the sexual reproduction 

 of the plants assigned to this order. Spermogonia are known in many 

 species and may function as they are known to do elsewhere. 



Order Hypocreales. This order shows a close parallelism with the 

 Sphaeriales as to perithecial form and arrangement. The two orders are 

 customarily distinguished from one another by the consistency and color 

 of the perithecia. In the latter order the perithecia are dark-colored and 

 leathery or brittle while in the former they are bright-colored (rarely 

 dark) and fleshy to leathery. There are border forms such as the genus 

 Melanospora which has sometimes been placed in one and sometimes in 

 the other order but which has been treated under the Sphaeriales in this 

 work. Miller (1941) did not recognize the validity of separating these 

 groups of fungi as distinct orders and included the family Hypocreaceae 

 as a distinct family in the Sphaeriales, but in a more recent paper (1949) 

 concludes that until further studies have been made on the structure and 

 development of the perithecia the Order Hypocreales should be retained, 

 except for Family Clavicipitaceae which definitely should be placed in the 

 Sphaeriales. The genera may be arranged with first the forms with 

 scattered superficial perithecia, then those with perithecia crowded on the 

 surface of a stroma, and those with perithecia buried in the substratum 



