CHAPTER V. — COMPARATIVE REVIEW. — ASCOMYCETES. 253 



It may be affirmed of the majority of the species which have just been con- 

 sidered, that they are imperfectly known, because no attempt has been made to 

 ascertain the entire course of their development. But some among them have not 

 only been observed in the mature state or occasionally grown from the spores, but 

 have been repeatedly submitted to long and careful observation and cultivation ; and 

 yet they are only known to produce the same supposed gonidial forms, and there 

 is no sign of ascocarps or of any other member of the development, which 

 the analogy of very similar forms in well-known species would have led us to expect 

 from them. The large species, Aspergillus clavatus 1 for instance, has never been 

 known to produce anything but gonidiophores ; the sporocarps like those of Eurotium 

 and Penicillium, which were to be expected from the structure of the gonidiophores 

 and of the mycelium, never made their appearance either in Wil helm's many experi- 

 ments in the artificial cultivation of the plant, which were made for the purpose 

 of determining this point and were conducted under a variety of conditions, nor in 

 many others which I have myself often repeated in the course of years. Botrytis 

 Bassii 2 is a very common insect-destroying Fungus, which in the character of its 

 vegetation is very like Cordyceps militaris, but resembles another Pyrenomycete, 

 Hypocrea rufa 3 , in the way in which it forms its exposed gonidia ; hundreds of 

 cultivated specimens of the plant have produced only the same organs bearing 

 gonidia, never a sign of perithecia ; my conjecture 4 , which has become an assertion 

 in Brefeld 5 , with regard to the latter has proved therefore to be incorrect. The same 

 must be said now of another insect-killing form which agrees very closely with 

 Cordyceps militaris in the mode also of forming its gonidia, and which I have 

 described under the name of Isaria strigosa 6 . Another instance which may be 

 noticed here is the universally distributed and repeatedly cultivated Oidium lactis ; 

 this plant never produces anything but the mycelium with cylindrical serially abjointed 

 gonidia 7 . The common Cladosporium herbarum, Lk. also should not be forgotten 

 in this connection. Further instances of this kind have been discovered in the course 

 of the investigations which have been made into the pycnidia. I refer to Zopfs 

 account of Fumago of which a resume has just been given. Brefeld 8 cultivated a 

 pycnidia-bearing form, a not uncommon parasite on the sclerotia of Sclerotinia, 

 under very varied conditions through more than a hundred successive generations, 

 without ever obtaining anything but the pycnidium-form. Similar results are 

 recorded for other species in Bauke's work on pycnidia ; Ehrenberg's Cicinnobolus, a 

 parasite on Erysipheae 9 , may also be quoted here, and it may be added that the 

 pycnidial forms mentioned here are so like others which undoubtedly belong to 

 typical Ascomycetes, that they may be readily mistaken for them. 



In view of these facts of experience the question again arises which was 

 discussed above in connection with the Mucorini and Peronosporeae whether we 

 have before us species which are only imperfectly known to us, and which under 



1 Desmazieres in Ann. d. sc. nat. ser. 2 (1834), II, tab. II Fig. 4.— K. Wilhelm, Dissert, p. 62. 



2 See Bot. Ztg. 1867. ° Bot. Ztg. 1869, p. 590. 



3 See Tulasne, Carpol. III. 7 See above at p. 67. 



4 Bot. Ztg. 1869, p. 590. 8 Schimmelpilze, IV, 122. 



5 Schimmelpilze, IV, p. 136. a Beitr. Ill, and above, Fig. 119. 



