SCIENTIFIC SUMMARY. 
103 
Diurnal and Nocturnal Expiration of Leaves . — The nature of the gases 
exhaled by plants during the day and night is still a question for botanists 
to solve. It has already engaged the attention of numerous physiologists 
and, among the number, of M. Corenwinder, who states as the results of 
his inquiries 1st, That leaves generally give off carbonic acid during the 
night ; but that the extent of this exhalation depends on the temperature — 
being reduced to nil when the thermometer approaches zero. 2ndly, In 
day -light, and especially if exposed to direct rays, the young shoots 
and buds give off carbonic acid — occasionally in considerable quantities, — 
thus showing that young leaves have not the power of absorbing and 
decomposing this gas. 8rdly, Adult leaves never expire carbonic acid when 
in the open air and receiving the light perfectly. 4thly, Coloured leaves 
do not differ from the ordinary green ones as regards the property of 
decomposing carbonic acid. M. Corenwinder experimented on specimens 
of hazel and copper beech, and found that they absorbed this gas in the 
daylight and exhaled it at night. 
Do Diatoms live on the Sea-Bottom at Great Depths f — In answer to 
this query, a note appears from Dr. Wallich in the August number of the 
“ Annals of Natural History.” He believes that these plants do not exist 
at considerable depths of the ocean. “ Although the soft parts are retained 
in specimens obtained from extreme depths, they differ materially both in 
aspect and qualities from those of diatoms known to be living.” It is very 
remarkable that diatoms brought up from extreme depths never exhibit 
any movements ; and as ordinary specimens possess a very decided power 
of locomotion, it seems fair to suppose that the former do not live at these 
depths. The coscinodisci which constitute the greater portion of the diatoms 
discovered in deep-sea deposits are essentially inhabitants of shallow water 
(from one to fifty fathoms), and they do not live in mud. According to 
Dr. Stimpson’s researches, the diatoms were found distributed all through 
the mud, a fact which Dr. Wallich conceives to be highly indicative of the 
absence of vitality. Moreover, it is exceedingly questionable whether 
diatoms ever form the food of rhizopods. 
The Leaf -Cells of Hymenophyllum have been subjected to microscopic 
examination by Professor Gulliver, and the results arrived at appear to 
support the view that II. Tunbridgense and If. Wilsoni are really distinct 
species. He states that in the former the leaf-cells are round, or nearly so, 
with an average diameter of s-f T of an inch, whilst in the latter they are 
oval, with an average long diameter of and a short one of of an inch. 
Especial stress is laid on the fact that in H. Wilsoni the cells are not only 
much larger but distinctly oval, and the terms sphcerenchyma and ovenchyma 
have been devised as diagnostics. Should the discovery prove to be correct 
it will be an additional aid to those botanists who delight in species, and 
will, we have do doubt, find its way soon into the ordinary floras. 
Vegetable Muscular Tissue. — The anther tube of the cynarese is supposed 
by Professor F. Cohn to have peculiar contractile povrers not unlike those 
of the flesh-particles of animals. It is remarkable that, as the Professor 
states, the contractions are due to simple elasticity, while the alternating 
elongations of the tube are special muscular movements. This view is not 
unlike that proposed by M. Claude Bernard in regard to contractile 
