Royal Microscoineal Society. 271 



observable in the walls of young axile cells of the Sphagnum 

 stem.* 



In most peduncular leaves the hyahne cells are less evident than 

 in those from other parts of the plant, and are often confined to the 

 upper third of the leaf. 



JDeveloyment of the Plant. — To the investigations of Nageli 

 and Hofmeister are we principally indebted for an account of this 

 interesting process. It not unfrequeutly happens that in floating 

 Sphagnum plants, whose capsules are submerged, that the spores 

 germinate in the capsule, where their dehcate pro-embryos are so 

 closely packed, that the whole contents are caked together into a 

 solid mass, which first becomes free by the breaking up of the 

 capsular wall, and in this condition swims about until the individual 

 plantlets have sej)arated from one another to estabhsh themselves 

 on some floating object and undergo further evolution. 



The spores of cajjsules maturing out of the water, germinate on 

 damp earth in two to three months. Prof. Schimper rarely noticed 

 the pro-embryonal cell break through the exospore in less than five 

 weeks. 



In water the pro-embryonal cell elongates and ramifies as 

 confervoid filaments formed of nearly globose cells, and the terminal 

 or some other cell becomes the mother cell of the young plant, 

 while the rest ramify and put forth brood-gemmae, which develope 

 into young plants, the radicles being always distinguishable by the 

 oblique commissural walls of the cells. 



The spores germinating on damp earth behave in quite a 

 difierent manner, the pro-embryonal cell goes on subdividing in 

 a horizontal plane, so that an expansion results resembling the 

 prothallium of Equisetum, or the perfect plant of Blasia or 

 Anthoceros. This hepaticine frond throws out radicles from the 

 under surface and margins, and from these again brood-gemmae 

 sprout out, fi'om which arise prothallia precisely resembling the 

 first. 



The first commencement of the young plant originates in a 

 tuberculoid aggregation of cells, some of which develope downward 

 into hair-like radicles, while the upper cell elongates and sub- 

 divides to form the young stemlet, some of the cells, laterally 

 becoming free, form the first rudiment of leaves. 



The young stem, at first transparent, soon acquires minute 

 chlorophyll granules, and a differentiation into medullary, ligneous, 

 and cortical layers is early set up. When it has reached a 

 height of about 5 mm., it begins to throw ofi" at the sides single 

 flagellar branches, which arise laterally from the uppermost leaves, 

 and are crowded together at the top of the stem. The branches 

 come off at every fourth leaf, as an obtuse bud of few cells, on 

 * Hofmeister, * Higher Cryptogamia,' pi, xvii., fig. 9 6. 



