SPECIAL MORPHOLOGY. 141 



The law of development might perhaps aid us in finding the distinguish- 

 ing differences in the development of the proembryo in the first named, 

 since between the first development of the propagating cell and the 

 actual development of the perfect plant a passing stage of transition is to 

 be met with, which manifests a certain analogy with the formations of 

 the groups of the Angiosporce. The further subdivision of the sexual 

 plants is, however, wholly based upon the law of development. The 

 Rhizocarpece, as the Athalamicce, constitute an admirable medial stage 

 between the Agamce and the Phanerogamce ; agreeing with the former 

 in this, that the propagating cell is developed to a new plant, without 

 any intermediate interruption*, and with the latter in their development 

 not being free, but being effected at first in the interior of a cellular 

 mass engendered by the parent plant. 



There are other characteristics denoting the internal and external 

 form of developed plants, which coincide in a remarkable manner with 

 those above given, and derived from the law of development ; these have 

 been already partially, but very imperfectly, treated of. The Angiosporce 

 may also be termed cellular plants (PL cellulares), since they afford no 

 indication of a current of sap passing through definitely arranged elon- 

 gated cells (vascular bundles). In like manner, their external form may 

 be defined as stemless (PL acaules, Thallophytce Endl.), as we have 

 not hitherto been able to detect any sharply defined morphological con- 

 trast between a lateral parenchymatic extension (leaves) and a body 

 uniting these (stem). In contradistinction the Angiosporce are designated 

 as vascular plants (PL vasculares), and as plants having stems (PL can- 

 lince, Cormophytce Endl.). The divisions of the Gymnosporce would 

 correspond to plants having simultaneous and progressive vascular bun- 

 dles ( 26.), and plants with or without an apparatus for propagation, and 

 finally characteristics drawn from the nature of the vascular bundles and 

 the morphology of the flowering portions of the plant might perhaps be 

 added to the Athalamic and Thalamic orders, but unfortunately we are 

 still deficient, especially with respect to the Rhizocarpecc, in the more 

 accurate investigations necessary to guide us. We cannot too frequently 

 repeat, that all our subdivisions are, and must be, regarded as merely 

 provisional, and as extremely deficient, as a correct classification can 

 only be derived from a complete knowledge of the law of comparative 

 development, from the attainment of which we are still infinitely far 

 removed. All that we can say is, that all divisions grounded upon cha- 

 racteristics which appertain in their nature only to a definite stage of 

 development, and do not stand in the most immediate connection with 

 the developing process, must either be decidedly false, or, at best, simply 

 accidental, and do not by their own value constitute the natural groups. 

 On the other hand, every classification must remain permanent that has 

 been derived from characteristics depending upon the law of develop- 

 ment. Thus the line of demarcation which has been laid down between 

 the Cryptogamia and the Phanerogamia will ever continue, even though 

 these divisions may not always be regarded as those possessing the 

 highest importance. The recent attempts to range the Cycadacece under 

 the head of the Ferns rests on such erroneous conceptions of vegetable 

 nature, and are based upon observations of so inessential a kind, that 

 they cannot be long maintained. In the same way, Monocotyledons and 

 Dicotyledons will always remain separated, and notwithstanding all the 



* They do not pass through a stage of seminal maturity, or slumber in embryonic 

 life. 



