6 LECTURE I. 



history of science, from a highly developed plant, from a plant the roots of which 

 every one knows as such, the essential root-properties of which are developed in 

 the highest perfection. The germinal shoot of the Almond is likewise that which 

 language has all along distinguished as a shoot. I name such organic forms which 

 present the essential peculiarities in great perfection, and from which therefore a clear 

 scientific consideration best proceeds, typical forms, and believe myself in this use of 

 the word to be completely in accordance with the original sense of the word Type. 

 When we now, proceeding from typical forms of organs, compare abnormal forms 

 with them, we find two different categories of these. For, on the one hand, we meet 

 in the lower regions of the vegetable kingdom with such forms of organs, especially 

 of roots and shoots, in which the organic differentiation generally is not yet so far 

 advanced as in the typical ones ; w^e have to do with feeble beginnings, which have not 

 yet attained to the typical standard. In this sense, we may term the roots of our 

 Boirydium and Mucor rudimentary roots, in so far as the word rudiment signifies a 

 state of beginning which has not yet attained to completeness. In strong contrast 

 to these rudimentary forms, we have to distinguish further the degenerate or reduced 

 forms. As it is to be assumed, from the standpoint of the theory of descent, that 

 the more perfect have gradually developed from the simple organisms, we are also 

 driven to the further assumption, that, in consequence of special modes of life, more 

 simply organised forms have again arisen from those more highly organised, and 

 this process we term degeneration, or reduction. This process is strikingly exhibited 

 when plants, which we must regard as originally always containing chlorophyll, 

 become parasitic. Since through parasitism they come into the condition of 

 absorbing organic material from wiihout, they cease to form it by decomposition 

 of carbon dioxide ; under these circumstances the chlorophyll is superfluous as an 

 instrumeht of assimilation, and in consequence of this, the whole remaining 

 organisation becomes simplified, so far as it is connected with the activity of the 

 chlorophyll; and since it is especially the shoots which are the bearers of the 

 assimilating organs, these lose, in parasites, together with the loss of chlorophyll, 

 all those peculiarities which arise from the activity of the chlorophyll, viz., the larger 

 development of surface, and the external segmentation connected therewith, and so 

 on. There then remains to the shoot only the second primary peculiarity, viz., to be 

 a bearer of fructification, and such we find to be the case in the third plant considered 

 above, the Mucor, as with most of the other fungi, and the phanerogams devoid of 

 chlorophyll. To recapitulate what has been said, we have, as the typical forms, the 

 highly organised ones which first offer themselves for consideration. Comparison with 

 these brings into notice, on the one hand, the rudimentary organs which have not 

 yet come up to the typical standard ; and on the other hand, we regard those organs 

 as degenerated, or reduced, which have been developed from typical forms by 

 simplification of their functions. 



It is, however, always very difficult so to form our general conceptions, that they 

 shall comprehend all the cases occurring in nature. So it is also here. For very often 

 organic forms are met with, with regard to which one knows not in which of these 

 categories they should be placed. For example, it is certain that the flowers of phanero- 

 gamous plants belong to the category of leafy shoots ; from a purely aesthetic point of 

 view, one might be led to consider them as the most highly developed form of shoot. 



