55 



himself is not uniform in his generally broad views of species. Of this we might 

 instance two examples — Didymium macrospermum and Trichia affinis; in the former 

 only distinguished from its ally by a flattened columella, and in the latter, the 

 absence of minute b'nes on the threads, which, when present, can scarce be detected 

 when magnified 500 diameters. 



Analytical keys, attached to each of the larger genera, will afiFord a clue to 

 what is regarded as essentials, and here our remarks will necessarily be of a 

 negative character ; and those who have been workine: on the old system will find 

 that they have much to unlearn. In the first place, colour is esteemed of no 

 specific value whatever ; hence, such names as Arcyria ciaerca, Arcyria punicea, 

 Arcyria incarnata, are discarded for others which bear no relation to colour. This 

 is an innovation of doubtful value, even supposing colour to be of no specific value; 

 it is always impolitic to increase synonyms without urgent necessity. Although 

 not prepared to contest this assumption, it may be asked why colour in the spores 

 is accepted as one of the fundamental divisions, if permanence of colour is only 

 found in violet ? and why violet should be permanent and ferruginous not ? In 

 all fungi, colour alone is too slight a basis for specific distinction, but, combined 

 with other features, it has an undoubted accessory value. For a very long time 

 Arcyria cinerea, Arcyria punicea, and Arcyria incarnata, have been determined 

 on the faith of their colour chiefly, and although we now recognize distinctive 

 features in the threads, this was not known, and therefore not taken into account 

 in the past. Rostafinski does not attempt to show that these external features of 

 colour and habit failed in correctly determining these species. There are no 

 citations of error into which authors may have been led by such a course, and this 

 is strong evidence that colour should not be wholly despised. It may be that in 

 escaping from one extreme, Rostafinski has sought refuge in another. Without 

 referring to special instances in which we fancy there is evidence of this, we will 

 be content to wait until experience indicates the happy medium. 



Another thing which has to be unlearnt, is the value of the stem. Many 

 species, as formerly described, were characterized as stipitate, and others as 

 sessile. This is met by the assertion that internal structure has demonstrated, 

 that, especially in such genera as Physarum and Didymium, the same species is 

 sometimes sessile, sometimes stipitate, and sometimes the sessile peridia are con- 

 fluent in an irregular form called a plasmodicarp. Hence, in many species we 

 have a stipitate form, a sessile form, and a plasmodicarp. In this view I am dis- 

 posed to concur. Since attention has been directed to this feature, I have found 

 a Craterium of the stipitate and normal form, with some peridia quite sessile, and 

 three or four individuals all running together into a plasmodicarp, on the same 

 dead leaf. This is an extreme and exceptional case, for Rostafinski himself has not 

 indicated this in the species of Craterium, in which the stem and peridium is 

 usually remarkably distinct, and I must confess that this experience influenced me 

 strongly in favour of Rostafinski's views. 



There are two other points to which I must allude, briefly, in conclusion. 

 In the genera Badhamia, as originally constituted, and in EnerthenemM and Enter- 



