424 LiniKEan Society. 



Read also *' Observations on the immediate causes of the Ascent 

 of the Sap in Spring." By Arthur Henfrey, Esq., F.L.S. &c. &c. 



Mr. Henfrey thinks that none of the causes generally stated, viz. 

 1. Endosmosis ; 2. Capillary Attraction ; and 3. Evaporation, are suf- 

 ficient to determine the first start of the sap. He objects to attri- 

 buting to the two first-named causes (endosmosis and capillary at- 

 traction) a primary part in the production of this phsenomenon, that 

 they cannot act M^here there is no outlet above, and vi^here conse- 

 quently no current can take place. As regards evaporation, he is 

 inclined to believe that it does not come into operation until a cer- 

 tain quantity of the sap has been absorbed and assimilated to the 

 new tissues. He refers to the precaution taken in the autumn to 

 cover up those portions of the plant which are exposed to the atmo- 

 sphere so as to protect them from its action, and to the fact that 

 buds burst forth, not from evaporation, but on the contrary, from 

 being gorged with moisture, as proofs that evaporation cannot be re- 

 garded as giving the primary impulse to the current of the sap. The 

 true cause of the ascent of the sap must, he thinks, be looked for in 

 the chemical changes which take place in the materials stored up in 

 the cells during the autumn. The insoluble grains of starch are con- 

 verted into soluble substances (dextrine and sugar) which are dis- 

 solved by the water always present in the tissues. A current is thus 

 produced by two concurrent circumstances, viz. the exhaust arising 

 from the syrup occupying less space than the materials from which 

 it was derived, and the endosmosis resulting from the increased den- 

 sity of the fluid contents of the cells. This chemical change Mr. 

 Henfrey believes to be brought about by the increase of temperature, 

 but whether it is immediately effected through the action of diastase 

 or other substances he is not at present prepared to give an 

 opinion. 



February 18.— W. H. Lloyd, Esq., in the Chair. 



Read a memoir " On Agaricus crinitus, L., and some allied spe- 

 cies." By the Rev. M. J. Berkeley, M.A., F.L.S. &c. &c. 



Mr. Berkeley refers to the Fungi of the Linnean herbarium as few 

 in number but in good condition, and comprising some remarkable 

 forms. Among these not the least interesting is the Agaricus cri- 

 nitus, which, together with a few allied species, it is the object of the 

 paper to illustrate. 



1. Lentinus crinitus, pileo late infundibuliformi repanrlo badio-rufo fibris 

 innatis apice liberis vix fasciculatis regulariter striate margine reflexo, 

 stipite sequali pallide sericeo-farinoso, lamellis acutis integris rigidius- 

 culis subdistantibus glandulosis decurrentibus postice anastomosan- 

 tibus. 



Agaricus crinitus, L. Sp. Plant, ed. 2. p. 1644. 



Hah. in ligno in America Australi, Rolander in Herb. Linn. 



The Agaricus crinitus of Swartz and Fries (figured and described 

 under the same name by Mr. Berkeley in the ' Annals of Natural 

 History ') is very distinct, and has since been named by Mr. Berkeley 

 Lentinus Swartzii. 



