SCIENTIFIC SUMMARY. 
89 
root-lice, -whlcli lie has minutelj described, constitute by far the greater 
portion of the disease. 
Boussingauli' s Recent Researches on the Chemistry of Respiration in 
Plants is referred to by a recent writer on the subject, Mr. Dewar, as being 
of great importance. His (Boussingault’s) observations on the amount of 
carbonic acid decomposed by a given area of green leaf seem to him to 
afford interesting data for a new determination of the efficiency of sunlight. 
By experiments made between the months of .January and October, under 
the most favourable circumstances, in atmospheres rich in CO^, one square 
decimetre of leaf was found to decompose in one hour, as a mean, 5-28 cub. 
centims. of 00*^, and in darkness to evolve during the same period of time 
0*33 cub. centims. of CO'^. In other words, one square metre of green sur- 
face will decompose in twelve hours of the day 63*36 cub. centims. of CO^, 
and produce in twelve hours of the night 3*96 cub. centims. of CO^. The 
quantity of carbonic acid decomposed does not represent the whole work of 
sunlight for the time, as water is simultaneously attacked in order to supply 
the hydrogen of the carbohydrates. Boussingault, in summing up the 
general results of his laborious researches on vegetable physiology, says, 
“ Si Ton envisage la vie v^getale dans son ensemble, on est convaincu que la 
feuille est la premiere etape des glucoses que, plus ou moins modifies, on 
trouve repartis dans les diverses parties de I’organisme ; que c'est la feuille 
qui les elabore aux depens de I’acide carbonique et de I’eau.” 
The History of Mucor Mucedo. — In his recent address to the Botanical 
Society of Edinburgh, Professor Wyville Thompson gave an interesting 
account of some of the forms of mould. He said that the life history of 
Mucor mucedo^ one of the commonest of the mildews, is not yet thoroughly 
known. In it the cells are simple and undivided, but each sporangium- 
bearer usually ends in several large sporangia. Under certain circumstances 
this sporangium-bearer sends out tufts of finely dividing twigs, each of 
which ends in a small sporangium, which, to distinguish it from the larger 
form, has been called a sporangiolum. At other times processes are pro- 
duced from the main cells which rise into delicate tubular branches, and 
give off globular cells which are called conidia — simple external spores, 
differing entirely in their character from the spores produced in sporangia ; 
and if this mould be grown in a solution in which it is fairly nourished 
without a full supply of oxygen gas, long fibres are produced which break 
up into a multitude of separate bead-like cells filled with protoplasm, and 
capable of reproducing the organism. 
The American Lichens have been partly recorded in a work on their 
an*angement, by Mr. Edmund Tuckerman, M.A. This work has just been 
published in America, but it will not be complete till the companion work, 
the Synopsis of the North American Lichens,” is finished and given to 
the public. This, however, will not be for some time, as the author is now 
travelling in Europe for the benefit of his health. The book is 8vo., and has 
about 296 pages. 
Hoio Mushrooms increase in Number . — At a recent meeting of the 
Academy of Natural Science of Philadelphia, Mr. Thomas Meehan, who 
appears to be one of the most industrious botanists in America, said he had 
observed this season that the spawn of the common mushroom {Agaricus 
