146 PROGRESS OF MICROSCOPICAL SCIENCE, 



meeting of the Linnean Society, held June 19th, which is thus ab- 

 stracted by ' The Academy.' He controverts the published views of 

 Duchartre that the " free central " placenta of Primulaceae is formed 

 perfectly free within the cavity of the ovary, and never at any time 

 has any connection with the ovarian wall, and finds on the contrary 

 that the placenta and ovarian wall separate from one another by a 

 process of differentiation. The ovules are of a very sim2)le structure, 

 consisting of nothing but a single integument covering the embryo- 

 sac ; there is no inner integument and no nucleus. The lower part of 

 the style consists of dense tissue absolutely impermeable to the pollen 

 tubes ; and even if these w ere able to enter the ovary in this way they 

 would be quite unable to reach the micropyle of the ovule, from its 

 close contiguity to the placenta. Professor Duncan has traced the 

 course of the pollen tubes from the base of the style through the loose 

 tissue of the placenta itself, from which they emerge in the imme- 

 diate neighbourhood of the micropyles of the ovules, which they then 

 enter. 



Tlie Mycelium of Agarics. — A paper on this interesting subject is 

 given in ' Grevillea' (July) by M. J. De Seynes. The mycelium, he 

 says, the elementary composition of which is very simple, found 

 under the soil, or under the debris of dead leaves or branches, affects 

 different appearances, generally white, sometimes yellow, and also 

 red. It is at times filamentous or silky {nematoid mycelium of 

 M. Leveille),* at times like felt (Jiymenoid mycelium of the same 

 author) ; finally, at times it becomes compact and solid, for a long 

 time regarded as a perfect fungus, and was called Scleroiimn ; this is 

 the scleroid or tuberculous mycelium of M. Leveille. This author 

 has also signalized the malacoid, or pulpous mycelium belonging to 

 some Physariacei, or to some Trichiacei, the fungoid nature of which 

 is actually contested. f The nematoid mycelium, which is more 

 frequently found amongst Agarics, varies extremely in appearance, 

 at times presenting itself like some rayed threads of silk, and prickly ; 

 at times ramified or dichotomous, like some radicular fibres, and at 

 times so thin that it is easily pulverized ; it certainly has its charac- 

 teristic value. Hoffmann draws from its absence, or its concrete 

 form, a conclusion which appears to us quite just. " That there is 

 more difference," says this author, " than the kind of development in 

 Amanita without a mycelium, which recals the Gasteromycetes, and 

 among which the mycelium is replaced by the veil, and some Agarics, 

 with a permanent mycelium in the form of Sclerotium, as for example, 

 Agaricus tuberosus." | One can, perhajis, jilace more value on the 

 permanence or annual disappearance of the mycelium, than to the 

 perennial, or to the annual or biennial life of the stem of Pha- 

 nerogams ; where the form of the organs of vegetation so notably 

 differs, it follows that they are monocotyledons or dicotyledons ; tlio 



* ' Annales des Sci. Nat.,' 2nd scr., t. xx., p. 78, &c. 



t The observations of Wigand (Pringslieim's Juhrbiicher) appear to me to 

 shake strongly the hypothesis of M. de Bany, as to the animal nature of these 

 small prodiiL-tions. 



X Hoflmann, ' loon. Analyt. Fuug.,' Htft !., 1861. 



