174 HOFMEISTER, ON 



It is a widely-spread notion that the pro-embryo of 

 mosses, irrespective of its entirely different physiological 

 nature, is distinguishable from the prothallium of ferns by 

 the fact that the former consists of confervoid cellular 

 threads, the latter of an ulva-like cellular superficies. I 

 was much surprised, therefore, when I found that certain 

 crisped vegetable formations resembling the prothallia of 

 the Equiseta or plants of Anthoceros punctatus and which 

 had grown as weeds amongst some unsuccessful sowings of 

 Lijcopodium Selar/o, proved to be the pro-embryos of a 

 moss, Sphagnum cuspidatum. 



Schimper (' Rech. sur les Mousses') has figured the 

 ramified rows of cells which are the first products of the 

 development of Sphagnum-spores when sown in water. 

 Afterwards the same observer noticed certain shoots pro- 

 ceeding from short lateral branches, during the vegetation 

 of the pro-embryo in water. These shoots are very pro- 

 bably the rudiments of leafy branches. When germinating 

 upon moist earth, one of the ramifications of the thread- 

 like pro-embryo becomes a cellular superficies (PL XVIII, 

 figs. 6, 8). The disposition of its cells fluctuates between 

 an arrangement in pairs and a simple cross-bar arrange- 

 ment ; this is caused by the repeated division of a single 

 apical cell, by means of septa perpendicular to the surface, 

 turned alternately to the right and to the left. The former 

 kind of cell-succession usually prevails. The copious rami- 

 fication of the pro-embryo appears sometimes truly, some- 

 times spuriously, dichotomous ; it is rendered indistinct by 

 the appearance of numerous adventitious basal shoots. A 

 vigorous pro-embryo forms a tangled tuft which it would 

 be lost labour to attempt to reduce to any regular system 

 of ramification (PL XVIII, fig. 5). 



Two phenomena distinguish these pro-embryos in a 

 remarkable manner from the prothallia of ferns and Equi- 

 setaceae. The crisped cellular surfaces are single throughout 

 their whole extent even after ten months' growth. The 

 parenchymatal tissue, from which the female organs of 

 reproduction are produced in the green prothallia, is never 

 seen. The base and the side-edges of the lobes of the pro- 

 embryo are furnished with thread-like processes which are 



