38 " ENDOSPERM." 



translators, it must be stated, do not pledge themselves, this word 

 appears with three, if not four, somewhat disparate significations, 

 thus: "Endosperm. (a) In Selaginella : tissue formed in the 

 cavity of the macrospore below the prothallium. (b) In Gymo- 

 sperms : prothallium within the embryo-sac (macrospore) ; secondary 

 endosperm may be formed as a nutritive tissue after the prothallium 

 is absorbed, (c) In Angiosperms : tissue formed within the embryo- 

 sac (macrospore) after fertilisation (commencing by division of the 

 secondary nucleus), and serving for the nutrition of the embryo." 



The confusion* however, appears in the body of the work ; and, 

 as it is at first apparently recognised and avoided, must be deliberate, 

 Speaking of the Selar/iiieltea, especially Selar/inella, and basing its 

 description on Pfeffer's in Hanstein's Bot. Abhand. iv. (1871), it is 



stated (pp. 285-6) that, "While the macrospores are still 



lying in the sporangium, their apical region is occupied by a small- 

 celled meniscus-shaped tissue, formed probably during the maturing 

 of the spores by the breaking up of a quantity of protoplasm 

 collected there. It is this tissue which subsequently produces the 

 archegonium, and is therefore the true prothallium; but some weeks 

 after the dispersion of the spores free cell-formation begins beneath 

 this earlier tissue in the cavity of the spore, which results in the 

 filling up of the entire cavity and the production of a large-celled 

 tissue, a secondary prothallium as it may be termed." 



This description, without the concluding words, is virtually given 

 in the first English edition of Sachs' * Text-book' (1875), where it 

 is illustrated, as in Goebel, with Pfeffer's now familiar figure showing 

 the well-marked " diaphragm " between the two tissues. There, 

 however, Sachs adds that the large-celled tissue, "Pfeffer, supported 

 by considerations with which I also agree, compares to the endo- 

 sperm of Angiosperms, and, following this analogy, calls by the 

 same name" (op cit t , p. 404). Goebel, however, merely adds (loc. 

 tit.) the following note : 



" Pfeffer compared this tissue with the endosperm of the Angio- 

 sperms, and gave it that name ; but since the homology of the two 

 formations must be doubtful as long as the processes in the macro- 

 spore of the Selayinellece are not better known than they now are, a 

 more definite term is preferable. It is probable that the contents 

 of the macrospore divide into two primordial cells, one of which 

 moves to the apex of the macrospore, and there produces the primary 

 prothallium ; while the other remains at first at the base of the 

 macrospore, and subsequently produces the secondary prothallium." 



This distinction in terms is not clearly maintained in the later 

 part of the work. It appears, in fact, to be more clearly expressed 

 in Sachs (p. 422), where, after acknowledging that the analogy of 

 the endosperm of Gymnosperms with the prothallium of the higher 

 Cryptogamia was first shown by Hofmeister, the author continues : 



" The processes which take place in the embryo-sac of Mono- 

 cotyledons and Dicotyledons appear somewhat different, and bear a 

 greater resemblance to w r hat takes place in the macrospore of 

 Selaginella. In this genus, besides the prothallium which produces 

 the arehegonia, there arises subsequently by free cell-formation 



