254 DIVISION II. — COURSE OF DEVELOPMENT OF FUNGI. 



certain conditions do really fill up the gaps in our knowledge, that is, are able to 

 produce the typical ascocarp of an Ascomycete; or whether there are species 

 which in their known characters do come near to typical Ascomycetous genera and 

 may even be included in them, but do not at present actually produce the ascocarp 

 of an Ascomycete. In the latter case a further question arises, whether and how 

 far the problematic defect comes from the loss of the capacity or from its having 

 never been possessed. The attempt to examine and answer these questions leads us 

 necessarily into the domain of conjecture, and forces upon us the reservations here 

 proposed. Every new unexpected fact may change the grounds of the decision. 

 If we begin with the second question from the stand-point of our present knowledge, 

 we must conclude that the plant has lost the capacity, as long as the views on the 

 unity and affinity of all the Ascomycetes and on their homologies and connection 

 with the Peronosporeae, which were developed above in section LXVI, are not shown 

 to be incorrect. This is the necessary result of what has been already stated and does 

 not require to be again explained. Whether the loss has in every case directly 

 befallen the species b under observation, or another n from which b is descended, 

 must remain an open question and is not an essential element in the matter. The 

 assumption of such a loss would also be in harmony with other known facts in the 

 Fungi which imply retrogression in the development of a species with excision of 

 certain members (see below in section LXXXII). Moreover there are distinctly observed 

 facts within the group in question, which enable us to form a clear idea of the way 

 in which this loss may be occasioned ; but these very facts themselves compel us to 

 be cautious and to leave it to time to give a decided answer to the second as well as 

 to the first of our questions. These facts are, first, that some species of Ascomycetes, 

 as has been already pointed out more than once, form their ascocarps only under 

 fixed and narrowly limited conditions, while they reproduce themselves by forming 

 gonidia under very varied conditions. Of this fact Penicillium, Peziza Fuckeliana, 

 Zopf's Fumago, and the species of Hypomyces described above, are examples. 

 Secondly, there are pleomorphic species which also show a marked tendency to the 

 reproduction of like forms when the conditions remain unchanged, that is, each 

 spore-form chiefly produces its own form again, more rarely a form of another kind. 

 Peziza Fuckeliana is an excellent example of this. If the gonidia of this Fungus, the 

 spores of ' Botrytis cinerea,' are sown in a good nutrient solution, grape-juice for 

 instance, the product is always a filamentous mycelium with copious formation of 

 gonidia. If the ascospores are sown in the same solution under exactly the same 

 conditions, a mycelium is developed with sclerotia, but gonidiophorcs never or 

 scarcely ever appear ; wherever they have appeared they have appeared singly, and 

 cases of the kind are highly exceptional and not free from suspicion on the score of 

 the purity of the sowing. If similar sowings arc made on suitable dead leaves of 

 Vitis or Castanca which have been boiled to free them as far as possible from 

 foreign spores, sclerotia are generally developed ; if ascospores are sown, sclerotia 

 only are formed without filamentous gonidiophores ; if gonidia are sown, the sclerotia 

 are accompanied by an abundance of gonidia which spring from the filamentous 

 mycelium. In cultures of the latter category single gonidiophores may certainly be 

 produced from a sowing of ascospores, just as they may be developed, as is well 

 known, from the sclerotia (see on page 224). The general result which is the 



