THE ARCHESPORIUM 107 



found to be the case in many of the Pteridophytes. But it was not 

 sufficiently recognised that between the two lies all the difference between 

 stratified and imperfectly stratified meristems. This point was brought 

 forward in iSg6, 1 in the proposition that "the study of the sporangia or 

 synangia of a plant should be carried out in the light of a knowledge 

 of the segmentation of its apical meristems," and the generalisation was 

 laid down that "where the apical meristems are distinctly stratified, the 

 structure of the young sporangium is stratified also : in those plants where 

 there is a non-stratified structure, with one or more initial cells, and 

 frequent periclinal division of superficial cells near the apex of stem, leaf, 

 or root, there the structure of the young sporangium is not distinctly 

 stratified." Such exceptions to the hypodermal position of the arche- 

 sporium as have been found among the Pteridophytes all fall under this 

 generalisation, and it may be added as a corollary that in all Vascular 

 Cryptogams investigated, the sporogenous tissue is ultimately referable to 

 the segmentation of a superficial cell or cells. This has been since 

 noted by \Vilson Smith,- who has accordingly suggested that the term 

 "archesporium " should be extended to these also, and he gives the definition 

 as follows: "The cell, or group of cells, whether superficial or hypodermal, 

 to which in a last analysis all the sporogenous portion of a sporangium 

 can be traced, ought to be called the archesporium." 



The use of the term " archesporium " has been discussed afresh by 

 Goebel in his Organography (p. 771). He first describes the case for the 

 anther of an Angiosperm thus : " In each of the four angles of the anther 

 a cell-row or cell-layer below the epidermis (hypodermal) divides by 

 periclinal walls. Of the cells which thus arise the internal form the 

 archesporium, the outer the ' schichtzellen,' which now divide still further 

 by periclinal walls." The archesporium is thus defined as the inner product 

 of the division of the hypodermal layer ; it gives rise neither to any part of 

 the sporangial wall nor to the tapetum, though, since these have a common 

 origin with it from the hypodermal layer, it is not clear why the latter 

 should not itself be styled the archesporium. Passing on to the Pteridophyta, 

 after noting how superficial cells give rise to the essentials of the sporangium, 

 and that the details are not uniform, he proceeds (/.<-., p. 774): "We 

 may then designate that superficial cell or cell-layer as archesporium which 

 sooner or later gives off sterile cells, while in the sporangia of Angiosperms 

 the archesporium is a cell-layer lying below the epidermis, which is already 

 differentiated : with this the above-noted differences in wall-structure of the 

 Pteridophyta and Gymnosperms on the one hand, and of the Angiosperms 

 on the other would correspond." This passage calls for the following remarks. 



In the first place, Goebel accepts the conclusion of Wilson Smith, 

 that since the sporogenous tissues of Pteridophytes are all referable in 

 origin to superficial cells, therefore those cells are to be recognised as 

 the archesporium. By accepting this conclusion, it may be presumed that 



1 Studies, ii., p. 8. - Bot. Gazette, vol. xxix., p. 325. 



