130 ' KEW PUBLICATIONS. 
was working in a field in wliich a large proportion of liis observations 
would be positive additions to science. 
Mr. Cooke, in this volume, restricts himself to these five Orders 
JEcidiacei^ Pitccmiceij C(Somacei, Peronosporei^ and ErysipJiei. He in- 
tersperses his entertaining narrative respecting their localities, appear- 
ances, influences on the supporting plant, etc., with details of their 
structure and classification ; and he adds, in an appendix, a systematic 
classification and description of the species of the various Orders referred 
to in the volume. This gives a scientific value to what without it 
would be simply a pleasing popular volume. Some of the species are 
described here for the first time ; the descriptions of many more are only 
to be found elsewhere in the recent botanical literature of the Continent, 
much of it inaccessible to the majority of British students ; and those 
that have already been published in England were included in Berkeley's 
supplementary volume to Smith's 'English Flora.' Since 1836, the 
date of that volume, nothing systematic has been done with these minute 
plants. Berkeley's ' Eungology ' and Cooke's ' Index Fungorum Bri- 
tannicorum ' are mere indices of the names of these microscopic Fungi. 
We have here a beginning of somewhat more satisfactory. ^Ye trust 
the volume will meet with the success it deserves, and thus encourage 
its author to take up the remaining Orders. 
Some of the remarkable recent discoveries are discussed at length in 
the work. One chapter is devoted to an examination of those obscure 
organs, the spermogones, — and another to the singular alternation of 
generations in Fungi, which is called dimorphism. ■ We shall conclude 
this notice by giving an example of dimorphism, somewhat condensed, ' 
from Mr, Cooke's pages. The common bean-rust, Uromyces appendix 
cnlata. Lev., towards the end of summer or beginning of autumn pro- 
duces oboval brownish spores. When these fall on the moist soil, each 
gives out a short curved tube that speedily produces three or four reni- 
form sporidia. The sporidium germinates on the epidermis of the bean 
by penetrating the wall of the cell on which it rests. The germ-tube 
having gained entrance, draws into itself the contents of the sporidium, 
and the empty external wall perishes. The germ-tube elongates and 
branches, becoming a mycelium and penetrating the intercellular spaces 
of the parenchyma. White spots on the leaf indicate the existence of 
the parasite beneath. Ere long spermogones in the form of small 
orange papilla? make their appearance on- the surface, and these are 
