BOT.-VOL. I.] CAMPBELL— NAIAS AND ZANNICHELLIA. 41 



young sporophyll of Equisetum. There is formed about 

 the base of the whole complex, a rudimentary sheath, ho- 

 mologous with that about the stem-apex, but usually incon- 

 spicuous and easily overlooked. Schumann (1892, p. 160) 

 denies the presence of such a sheath, although both Irmisch 

 and Eichler have described it. In a number of the speci- 

 mens examined by me, however, there was no question as to 

 its presence, although, as usual with the sheaths in the main 

 stem, one side (the inner) is usually higher than the other; 

 so that here the outer margin may be almost or quite abortive. 

 It is, however, extremely likely that Schumann (1. c.,p. 161) 

 really saw this but mistook it for anther structure. He de- 

 scribes what he calls a " Vorblatt," which, as he says, is 

 never found in the " branch from the upper sheath-leaf." 

 From a study of Schumann's figures and my own prepara- 

 tions, I am strongly inclined to believe that what Schumann 

 supposed to be a special subtending leaf is in reality the 

 inner margin of the sheath at the base of the staminal com- 

 plex, which was not developed, or only slightly so, on the 

 outer side. 



The origin of the sporogenous tissue of the anther is not 

 easy to trace, as the archesporial cells- are at first hardly dis- 

 tinguishable either in form or contents from the adjacent 

 cells. As soon as they are recognizable there is already a 

 group of them whose relation to each other is not entirely 

 clear. The archesporium is developed at four points, and 

 in this respect, as well as in the general structure of the 

 older anther, Zannichellia is very different from Naias 

 jlexiUs and resembles more the typical Angiosperms, with 

 their four loculi in the anther. Whether these four loculi are 

 to be considered as each homologous with the single one in 

 Naias jlexilis, or whether the latter is to be considered as 

 made up of four confluent loculi, is a question which it is 

 not now possible to answer. It will first be necessary to 

 study the development of the anther in some species of 

 Naias which is normally quadri-locular. 



The anther grows rapidly and becomes longer propor- 

 tionately, and with this there is a rapid growth and division 



