LECTURE XLII. 



THE ORGANS OF REPRODUCTION {Continued)'. 

 HETEROSPOROUS VASCULAR CRYPTOGAMS; GYMNOSPERMS; ANGIOSPERMS. 



There existed during previous geological epochs Horsetails with two kinds of 

 spores ; but the species are extinct. Nevertheless we have still two small families of 

 Pern-like plants, mutually very distinct, which in spite of their great differences 

 are usually grouped together under the absurd name Rhizocargeae : these are the 

 Salvine se and the Marsiliea e in which are formed two kinds of spores- entirely 

 different in nature, and the same peculiarity is again met with in the case of the third 

 great subdivision of the Vascular Cryptogams, namely the T.ycnp ndia.r.eaR (Dicho- 

 tomecB). Here also there are two very different families, the Selaginella e and the 

 Jsoeteae, in which two kinds of spores are produced. I cannot here suppress the 

 remark that it harmonises Httle with Darwin's views when we see repeated in three 

 very different classes of the vegetable kingdom, with otherwise similar spores, a 

 phenomenon so important as is the production of two kinds of spores with their 

 consequences. Certainly it cannot be explained by natural selection in the struggle 

 for existence. This however simply by the way. 



The consideration of a few cases where the development of two kinds of spores 

 takes place is essential to the reader, since a satisfactory insight into the reproduction 

 of the Coniferse (Gymnosperms) and in fact of the true flowering plants can only be 

 attained by this means. One of the most magnificent results in the province of Embryo- 

 logy was Hofmeister's demonstration in 1851 of the fact that the formation of seed in 



' As in the first eleven lectures, which are to be regarded simply as an organographical 

 introduction to the physiology proper, so also in the two preceding lectures my wish has been only 

 to give a very condensed sketch of the organography of the reproductive apparatus. From the 

 astounding variety of materials to hand only a few examples could be taken into account ; those 

 who desire more detailed information concerning the organisation of the reproductive system, and 

 (what can scarcely be avoided here) as to their phylogenetic or systematic connection in the various 

 subdivisions of the vegetable kingdom, will find in my 'Text-book of Botany' a rapid but very 

 thorough survey in this connection. Still further details, especially with respect to the most recent 

 observations on the Algse and Fungi, and the remarkable developmental relations of the sporangia 

 of the Cryptogams to those of the Phanerogams, are to be found in Goebel's new edition of my text- 

 book, which has just appeared under the title ' Grundziige der SysUmatik.' There is an English 

 edition published by the Clarendon Press, Oxford. 



