THE HIGHER CKYPTOG AMIA. 171 



difficulty. The investigations of Hedwig and his successors 

 can be so easily repeated in many species, as, for instance, 

 Funaria hygrometrica and Barbula muralis, that it would 

 be waste of time to give a description of the phenomena. 

 I will mention only some peculiarities which are not so 

 well known. 



The threads of the pro-embryo, whether they arise 

 from the development of a spore, or from a cell of 

 the surface of the stem or of a leaf*, exhibit in many 

 species two very different modifications of development. 

 The principal ramifications of the confervoid rows of cells 

 are filled with assimilated matter, and contain very 

 numerous chlorophyll bodies ; their longitudinal growth, 

 which results from repeated transverse divisions of the 

 terminal cell, is unlimited. The lateral ramifications of 

 these principal branches of the pro -embryo have only a 

 limited growth ; the terminal cells, when they cease to 

 divide, assume a conical form. Moreover the lateral 

 branchlets ramify in a complicated manner. Their con- 

 tents are far less concentrated, their transverse diameter 

 narrower, their chlorophyll more inclined to a yellowish 

 tinge than is the case with the principal branches. These 

 latter only are capable of producing true germs or leafy 

 axes. The principal branches of the pro-embryo may, 

 perhaps, be compared to stems ; the lateral branches with 

 limited growth to leaves. These phenomena are very 

 remarkable in the pro-embryo of Racomitrium ericoides. 

 Here, owing to their peculiar habit, the lateral shoots of 



* I wish to add a few words as to the meaning of the expression " pro- 

 embryo." By the word "embryo," is meant the bud capable of developing 

 leaves and roots. Thus, we speak of the embryo of the onion, the potato, the 

 hop. Now, when we find in the vegetable kingdom organs which differ from, 

 and are of an essentially simpler structure than the leafy stem-rudiments which 

 afterwards spring from them, but which must normally and necessarily in the 

 course of their development produce embryos, I consider that I am justified in 

 calling these organs " pro-embryos." Thus, I designate as a pro-embyro the proto- 

 nema of a moss, whether it owes its origin to the germination of a spore or to the 

 independent development of an individual cell of the leaf- bearing plant. I treat 

 in the same manner the suspensor of Selaginella, of the Coniferse, and of the 

 phanerogamia. On the other hand, I do not designate as a pro-embryo the 

 body which is produced directly from the germination of the spores of ferns, 

 Equisetacese, Rhizocarpese, and Lycopodiacese, and which bears antheridia and 

 archegonia, usually only the latter. This organ I call a " prothallium." 



