370 SCIENCE PROGRESS. 



and remain as somatic cells. In the Liverworts as we pass 

 to the higher terms of the series, we see as in the Antho- 

 ceroteae the spore-mother-cells entangled in a mesh-work of 

 sterile cells; here is truly an approach to a septate condition,, 

 but even here the final step is not taken. 



With these ideas before us we pass to the organisms 

 on the other side, and inquire whether in them there is 

 evidence of sterile cells dispersed through the sporogenous 

 mass : of incomplete septation : of formation of septa in 

 organisms whose near relatives show none : or of actual 

 conversion of tissues, of common origin and position with 

 those which form spores, into sterile masses. Such evidence 

 there certainly is, though much of it is open to various, 

 interpretations. 



First, it is essential to obtain proof that complete septa- 

 tion can, and does occur. This is shown in the case of 

 certain anthers of Angiosperms: in the Onagraceae the anther 

 is commonly of the quadrilocular type, but in certain 

 genera, not differing otherwise in vital points, the loculi 

 are found divided by sterile septa into two or more cavities : 

 the tissue which forms the septa has been traced as of 

 common origin with the sporogenous cells. The conclusion is 

 therefore justified that in these cases sterile partitions have 

 been formed by conversion of potential sporogenous tissue 

 into tissue of the septum. Such a process is found also in 

 the Mimoseae, Myrsineae, Rhizophoreae, Loranthaceae, Raf- 

 flesiaceae : it is therefore no isolated phenomenon, but one of 

 wide occurrence in Angiosperms. 



The result is a partitioned body, more or less like the 

 synangia which are so common a feature in certain Eu- 

 sporangiate Pteridophytes, such as Opkioglossum, Dancea, 

 Psilotum and Tmesipteris. It would lead us too far to go into 

 the detailed evidence with regard to these plants : it is, or will 

 be, fully set forth elsewhere. From study of various Pteri- 

 dophyta we arrive at the position that sterile cells are 

 frequently found dispersed through their sporogenous group 

 iyEquisetum, Opkioglossum, Psilotum, Tmesipteris, compare 

 Liverworts) ; that incomplete septa, such as those present in 

 certain of the anthers above quoted, are found also in 



