LYCOPODIACEM. 



40: 



be sufficient to divide the Lvcopodiacece into two classes, and to include the 

 genera L}copodium, Psilotum, Tmesipteris, and the less known Phylloglossum in 

 the highest class of higher Cryptogams, if the difference were an actually existing 

 one ; but at present it rests only on an insufficient knowledge of these genera, which 

 are otherwise closely allied to Selaginella in the mode of formation of their tissue, 

 in the dichotomous branching of their stem and root, in the nature of their leaves, 

 and in other characters. We must therefore, until our knowledge is more complete, 

 consider all these genera as members of one class. 



The Microspores of Isoetes and Selaginella do not produce the mother-cells of 

 the antherozoids immediately from their contents, as was formerly thought. To the 

 treatise of Millardet mentioned in the foot-note we owe our knowledge of the fact, 



Fin. 301. — Germination of the microspores of Isoetes lacustrts (after Millardet). A and C microspores seen on the 

 ri^ht side. A' and Don the ventral face ; A and /> show the fonnation of the antheridium, 65 its dorsal cells, ^^ its ventral 

 cells, C and D the fonnation of the antherozoids, /3 and 5 have disappeared; 7/ is the vegetative cell (prothalliiini of Mil- 

 lardet) ; <t—/" (development of the antherozoids (.-/—/> and a—d x 5S0, c andy X 700). 



so important in connection with the relationship of the higher Cryptogams to the 

 Gymnosperms, that at the period when the microspores are ripe, their contents are 



smooth, while the upper has numerous grooves and protuberances. In these grooves the antheridia 

 and archegonia are situated. A vertical section through the prothallium shows that the cellular 

 structure is formed of three regions ; the uppermost, in which the antheridia and archegonia are 

 developed, consists of thin-walled cells poor in cell-contents ; the cells of the middle layer are rather 

 smaller, and filled with dark granular contents rich in fatty matter ; those of the lowermost region 

 are somewhat elongated parallel to the surface, and their contents are turbid and finely granular. 

 Starch does not appear to be present in any part of the prothallium. The antheridia are filled with 

 innumerable antherozoid-mother-cells ; the antherozoids are only slightly twisted and are stout 

 compared with those of Selaginella. The archegonia were not observed, but the position they would 

 occupy was indicated by that of the gei-minating plants, and it seems probable that they are not sunk 

 completely in the tissue of the prothallium. In general only one embryo is produced from each 

 prothallium, but it appears that a second may be produced from a second prothallium when the 

 first is abortive. The reproduction of Lycopodium appears, therefore, to bear the greatest resem- 

 blance to that of Ophioglossaceee. Berkeley remarks (Introd. to Crypt. Bot. p. 549) that Ophio- 

 glossece ' are plainly connected with Clubmosses by Rhizoglossum, a Cape genus which has precisely 

 the habit of Phylloglossum (Lycopodiacea?), consisting of a few subulate leaves and a pedunculate 

 spike of sporangia.' — Ed.] 



Dd 



