56 Linnean Society. [Feb. 4, 



vanced by Schleiden as to the origin of the bands and fibres 

 in the cellules and vessels of plants. Being anxious to ascer- 

 tain whether the bands exist at an early period, the author had 

 recourse to the examination of a young undeveloped frond, about 

 two weeks old, and he was much gratified by finding his previous 

 suspicions fully confirmed ; the cellules then being of a uniform 

 transparency, presenting neither bands nor dots, but furnished with 

 a distinct cytoblast or nucleus, which was found to have entirely dis- 

 appeared from those cellules in which the incrustating matter was 

 visible, proving that the incrustating matter is formed at the expense 

 of the nucleus. The matter forming the bands is continuous, and is 

 evidently not formed by a coalescing of spiral fibres, as some might 

 suppose ; for it is perfectly solid, and shows no disposition to un- 

 roll or to break up into fibres. The bands most probably originated 

 from the shrinking up of the incrustating substance, which at first 

 was equally diffused in a fluid state over the walls, and which, from 

 the mere effects of consolidation, aided by the distention, and per- 

 haps enlargement of the cellule, would naturally leave portions of 

 the primitive membrane uncovered. That the dotted and reticulated 

 vessels in Cycadece are of the same nature, and originate in a similar 

 way as the cellules just described, there seems no reasonable ground 

 to doubt. The parenchymatous cellules in Cycas circinalis, glauca, 

 and speciosa resemble those of Zamia and Encephalartos in having 

 their walls of a nearly uniform thickness and transparency, being 

 but rarely furnished with a few elliptical obliquely transverse spaces 

 or dots. The cellules in Cycas revoluta vary both in size and 

 structure, some being three or four times longer, whilst others are 

 still longer and narrower, and furnished with more numerous and 

 much smaller dots, which are not confined to the sides, but are 

 disposed around the tube. These last, which have been observed 

 also in Cycas glauca and circinalis, present an evident transition to 

 the dotted vessels. 



The whole of the Cycadete are supplied with numerous gummife- 

 rous canals, often of great length, and uniformly furnished with 

 distinct cellular walls of considerable thickness, and which have 

 been accurately described and figured by Professor Morren in a 

 recent memoir. 



Notwithstanding the analogies presented by their reproductive 

 organs, the author considers the Cycadecs as related to Coniferee 

 only in a remote degree, and that they constitute the remains of a 

 class of plants which belonged to a former vegetation. 



