1900] SPOROPHYLLS. AND SPORANGIA OF ISOETES 235 
nature of the sporangium rudiment as a transverse row of cells, 
his account is surprisingly accurate when the imperfect methods 
of sectioning and staining of that time are taken into considera- 
tion. 
According to Hegelmaier (2) and Tschistiakoff (1) the 
sporogenous tissue is differentiated out of a considerable mass 
of deep-lying meristem between the epidermis and the vascular 
bundle. 
Goebel (1) agrees substantially with the two preceding 
authors, but is more explicit in his description. The Anlage of 
the sporangium according to him is a group of cells of the leaf 
base, chiefly the three upper layers. The outer layer gives rise 
to the sporangium wall, and the hypodermal layer to the arche- 
sporium from which all the spore mother cells, trabeculae, and 
tapetum are derived. Goebel’s account, as confirmed and 
restated by Sadebeck (1) in Schenck’s Handbuch der Botanik, has 
formed the basis of all the text-book descriptions of the sporan- 
gium of Isoetes written since that time. 
The latest student in this field is Bower (5), whose descrip- 
tion is confirmatory of Goebel’s except that he traces the origin 
of the sporangium to a group of superficial cells. This differ- 
ence, however, is of the very greatest importance. For whereas 
the derivation of the archesporium by periclinal divisions of 
Superficial cells is the rule in Pteridophytes, the origin of the 
Sporogenous tissue from a hypodermal layer separated from the 
beginning from the epidermis is a spermatophyte character. The 
result of Bower’s work then is to put Isoetes in line with other 
Pteridophytes in respect to the origin of the archesporium. 
My own results are in the main confirmatory of Bower’s as 
to the origin of the sporangium, though with variations in minor 
details which may be due to specific differences (Bower studied 
Z. lacustris) ; but as to the later stages of development, especially 
si the megasporangium, I cannot make my observations harmo- 
nize with any accounts hitherto written. 
It will, of course, be apparent, when so many discrepancies 
appear in the descriptions of different investigators, that the 
