SCIENTIFIC SUMMARY. 
197 
belonging to the Umbelliferse, and hence that it may be said to constitute a 
form of venation peculiar to this order, and to give a character to it which 
does not belong to other orders of plants. 5. That when a leaflet is placed 
between two pieces of glass, and examined with a low power of twelve 
diameters, the vein becomes distinctly visible. 6. But that it is also visible, 
even to the naked eye, in certain of the species — Eryngium onaritimum, 
E. campestre, Silaus p)ycitensis, &c. 7. And finally, that it is possible that a 
more attentive study of the venation of leaves might prove of considerable 
assistance in the classification of plants. — Vide Quarterly Journal of Micro- 
scopical Science, January. 
The Proper Vessels of Plants . — M. A. Trecul laid a memoir before the 
French Academy, at its meeting on March 9, in which he adds new facts to 
his original observations on the subject of the proper vessels. 
Polymorphism in Lichens. — Those of our readers who were interested in 
Dr. Braxton Hicks’ valuable paper on the lower Algm, which appeared in 
one of our back numbers, will be glad to learn that the philosophical views 
therein expressed — as to the possibility of many of the so-called species 
being developmental phases merely, have been fully corroborated in an 
excellent article by Dr. Lauder Lindsay. This article appears in the last 
Microscopical Journal, and the following observations which we quote from 
it show that Dr. Hicks is not alone in viewing many of the so-called species 
with suspicion : — There are many other forms of polymorphism in the repro- 
ductive organs or bodies of lichens, which are of great interest to the philo- 
sophical botanist. Our knowledge thereof consists, however, of fragmentaiy 
and isolated observations, casually made in different parts of Europe. They 
are not more numerous, I believe, simply because Lichenology has been 
hitherto almost exclusively studied by mere systematists — by species-makers, 
who describe phases of plant-life as species, genera, or groups ! Philosophical 
biographers of lichens have been very few — physiologists, I mean — who 
have given themselves the time-consuming, and often fruitless, task of 
studying all the phases of development of even a single lichen. Such labour 
I believe to be of the most recondite character ; and it is, perhaps, not sur- 
prising that lichenologists should always have preferred the infinitely more 
easy task of discovering and describing so-called neiu species, three-fourths, 
however, whereof will, probably, ultimately be shown by the philosophical 
lichen-biographer to be merely forms or conditions of groivth, undeserving, 
for the most part, separate nomenclature.” 
The Eevelopment of Agaricus . — Professor Oersted’s fine memoir, which had 
remained so long untranslated, has been reproduced in English by the editor 
of the Microscopical Journal, to whom naturalists are much indebted. The 
following are a few of the more striking conclusions at which the author has 
arrived : — 1. The mycelium of this fungus is formed of long dichotoniously 
branched tubular cells, without septa, united into a loose web, and with so 
thin and soft a membrane that it has almost quite the character of a mucous 
membrane. 2. From the mycelium cells proceed both vegetative organs of 
propagation or bud-cells and organs of fructification. 3. The organs formed 
as bud-cells have been previously described as an independent species amongst 
Hyphomycetes {Cephalosporium macrocarpuni) , 4. The female organ of 
fructification is a reniform oogonium, which is curved down against the 
