ON THE HIGHER CRYPTOGAMOU3 PLANTS. 123 



less complex, and the duration of the fruit-bearing shoots is little longer than 

 that of the fruit itself. On the other hand, the ramification of ti)e prothallium 

 of the Equisetaceae is exceedingly complicated ; its duration is even equal to 

 that of a single shoot. 



" It is a circumstance worthy of notice, that in the second generation of 

 Mosses, as of the Filicoids, destined to produce spores, more complex thick- 

 enings of tlie cell-walls regularly occur (teeth of the peristome of Mosses, 

 wall of capsule and elaters of Liverworts, vessels of Filicoids, &c.), while in 

 the first generation, springing from the spores, such structures are found only 

 rarely and as exceptions. 



" The manner in which the second generation arises from the first, varies 

 much more in the Filicoids than in the Mosses. The Polypodiaceae and 

 Equisetacese are hermaphrodite ; the Rhizocarpeae and Sehtgineiiae monoe- 

 cious. All the Filicoids agree in the fact that the first axis of their embryo 

 possesses but a very hmited longitudinal development; that it is an axis of 

 the second rank which breaks through the prothallium and becomes the main 

 axis ; further, in the end of the axis of the first rank never becoming elon- 

 gated in the direction opposite to the summit. All Filicoids are devoid of a 

 tap-root, and possess only adventitious roots. 



" In more than one respect does the course of development of the embryo 

 of the Conifers stand intermediately between those of the higher Cryptogams 

 and the Phanerogams. Like the primary parent-cell of the spores of the Rhi- 

 zocarpeae and Selaginellae, the embryo-sac is an axile cell of the shoot, which 

 in the former is converted into a sporangium, in the latter into an ovule. In 

 the Conifers the embryo-sac also very early becomes detached from the cel- 

 lular tissue surrounding it. The filling-up of the embryo-sac with the albu- 

 men may be compared with the origin of the prothallium in the Rhizocarpeae 

 and Selaginellae. The structure of the 'corpuscula' bears the most striking 

 resemblance to that of the archegonia of Sahinia, still more to that of the 

 Selaginellae. If we leave out of view the different nature of the impregna- 

 tion, in the Rhizocarpeae and Selaginellae by free-swimming spermatic fila- 

 ments, in the Coniferae by a pollen-tube (which ^jer/iaps developes spermatic 

 filaments in its interior), the metamorphosis of the embryonal vesicle into the 

 primary parent-cell of the new plant in the Conifers and Filicoids is solely 

 distinguished, by the latter possessing only a single embryonal vesicle which 

 completely fills the cavity of the central cell of the archegonium, while the 

 former exhibits very numerous embryonal vesicles swimming in it, of which 

 only one pressed into the lower end of the ' corpusculum' becomes impreg- 

 nated. The embryo-sac of the Conifers may be regarded as a spore which 

 remains enclosed in its sporangium ; the prothallium which it forms never 

 comes to light. The fertilizing matter must make a way for itself through 

 the tissue of the sporangium, to reach the archegonia of this protliallium. 



*' Two of the phaenomena which led me to compare the embryo-sac of the 

 Conifers with the large spores of the higher Cryptogams, are common also 

 to the embryo-sac of the Phanerogams : the origin from an axile cell of the 

 shoot, and the independence of the surrounding cellular tissue (so striking, 

 for example, in the Rhinanthaceae, through the independent growth of the 

 embryo-sac). By their pollen-grains producing tubes the Conifers are closely 

 connected with the Phanerogams, from which they differ so much in the course 

 of development of their embryo-sac and the embryonal vesicles. The sepa- 

 ration of the prothallium of the Conifers into a number of independent sus- 

 pensors,is aphaenomenonof a most peculiar kind, having no analogue through- 

 out the vegetable kingdom." — (^Loc. cit. pp. 139-41.) — A.H. Dec. 16,185 1. 



