SPECIAL MORPHOLOGY: LIVERWORTS. 169 



connection with the plant they are converted into small cellular 

 corpuscles, often surrounded by a peculiar crescentic cup-shaped or 

 flask-like elevation of the upper cellular layer (conceptaculum), as, 

 for instance, in the Marchantia. 



Until a very recent period, Liverworts (with the exception of a few 

 individual and unimportant researches) were merely objects of petty 

 species-making, it is only in our own day that two men, Lindenberg * 

 and Gottsche f, have zealously directed their minds to the subject ; to the 

 latter we are especially indebted for the interesting facts he has con- 

 tributed concerning these beautiful plants. I cannot myself venture to 

 say much on the subject, as I have not as yet had any opportunity of in- 

 stituting very extended investigations into the nature of these plants. 



More comprehensive investigations into the history of their develop- 

 ment were first afforded us by Gottsche (loc. cit.\ relative to Junger- 

 mannia bicrenata, Preissia commutata, Blasia pusilla, Pellia epiphylla, 

 to which we may also add the observations of Mirbel on the Marchantia 

 polymorpha. These acceptable contributions, however, still leave much 

 to be desired, particularly in reference to the origin of the cells and the 

 development of the leaves. From what has been published, we learn that 

 the development of the spores exhibits no such sharply defined type as in 

 the succeeding groups of the Agamce, at least not such as in the Mosses 

 and Ferns. 



The forms unfolding themselves manifest as yet a very vague character. 

 In the lower, leaves are wholly wanting ; and here, consequently, the pre- 

 dominance of fancy over observation, which we so frequently meet with, 

 has caused much to be said of the notion of the fusion of the leaves in the 

 stem. As no leaves are present in the Jungermannia multifida, none are 

 to be found, but in this case they are just as little fused into the stem 

 as in Melocactus and Euphorbia meloformis. It does not at all follow 

 that a plant must have leaves' and a stem, but it is certainly purely 

 in accordance with our experience to assume that some plants exhibit 

 two essentially different processes of development, and that from these, 

 two essentially different forms, as leaf and stem, may appear: where 

 nature abides by only one of these processes of development, a stem 

 without leaves will alone occur ; and where the process is again different 

 from this, neither stem nor leaf will be found. If we do not seek for 

 definite conceptions of the history of the development of a plant by an 

 inductive course, we may give free scope to our fancy, but we shall never 

 learn to understand nature. 



In the Angiosporce we could not distinguish individual growth and 

 individual repetition by gemmation, on account of the morphologically 

 undefined character. Similar examples occur in the Liverworts in the 

 ramification of the flat stem without any preceding formation of buds. 

 In the Mosses no case of the kind occurs, as far as I know. In the Ferns 

 and the Rhizocarpece a few instances present themselves ; but not after- 

 wards, unless we except the case of the Podostemece> with which we are 

 still very imperfectly acquainted. 



The forms of leaves appear only gradually in this group. In the 



* Lindenberg, Ueber die Riccieen, Nov. Act. L. C. xviii. 



f Gottsche, Anatomisch-Physiologische Untersuchungen iiber Haplomitriwn Hookeri, 

 Act. A. C. L. C. N. C., vol. xx. pt. i p. 207. At the present moment, unfortunately, 

 another excellent set of observations by the same author are not yet in the hands of the 

 public. 



