988 RECORD OF CURRENT RESEARCHES RELATING TO 



In the typical FilicineaB, the course of development of the sporan- 

 gium is well known. A single epidermal cell of the leaf swells out, 

 forming the mother-cell of the sporangium, within which a pedicel- 

 cell is tirst of all separated by a septum from the mother-cell of the 

 capsule. Tliis last then divides into four parietal and one central 

 cell, the latter being the archespore, distinguished by the largo 

 amount of protoplasm that it contains, from which the spore-forming 

 tissue is developed. The archespore then forms two layers of so-called 

 " mantle-cells," surrounding the central cell, and corresponding to 

 the " tapcten-cells " in the pollen-sac of phanerogams. The arche- 

 spore is, therefore, in the typical FilicineiB, a Jiypodermal cell. 



In the Ophioglossacete, the process is somewhat different, the 

 sporangium originating not from a single cell, but from a mass of 

 cells. The young sporangia of ButrycMum Lunaria are masses of 

 cells forming a hemispherical protuberance. Notwithstanding the 

 contrary statement of Eussow, the archespore from which the sporo- 

 genous tissue is developed is here also, as in typical ferns, a single 

 cell, although occupying a different position. The archespore is here 

 the terminal cell of the axial row which lies beneath the still uni- 

 lamellar epidermis, and is distinguished from the adjacent cells by 

 its abundant protoplasm, soon also surpassing them in size. The 

 mantle-cells are formed by divisions in the epidermal cell which lies 

 immediately above the arcliespore. The archespore at the same time 

 divides into four daughter-cells. 



The development of the sporangia of the Equisetacese closely 

 resembles tliat of Botrychium. The archespore is here also the 

 terminal cell of a hypodermal row, formed on the under side of the 

 sporangiojjhore, and is originally unicellular ; the sporogenous tissue 

 resulting from its division. In specially vigorous sporangia it is 

 possible that it may occasionally be bicellular, and it at all events 

 divides longitudinally at a very early period into two cells. The 

 mantle-cells are formed in the same way as in Botrychium, but are not 

 so sharply defined. 



Closely resembling the processes above described is that in Lyco- 

 podium (Selago). The sporangium arises at the base of the leaf, and 

 attains its subsequent axillary position by displacement ; it originates 

 from a few cells. The centre one of these grows the most vigorously, 

 and subsequently gives rise to the archespore. As in Botrychium and 

 Equisetum, the archespore, distinguished by its size, abundant proto- 

 plasm, and the power of swelling of its cell- wall, is the teiminal cell 

 of an axial row lying beneath the wall of the young sporangium. In 

 L. annotinum and other species the processes appear to be the same. 



In Isoetes, the origin of the sporangium is a group of cells at the 

 base of the leaf. In its earliest stage the archespore, both of the 

 macrosporangium and the microsporangium, is here not a single cell, 

 but is composed of a layer of cells. A difference then sets in between 

 the development of the microsporangia and macrosporangia. In the 

 former the archespore- cells elongate in a direction vertical to the 

 surface, and divide by septa. No difference is yet discernible 

 between the sterile and fertile cells ; but subsequently some rows 



