LECTURE XLVI. 



THE OBJECT OF FERTILISATION. APOGAMY'. 



There are many plants which, like Mammals, Birds, and other highly organised 

 animals, reproduce themselves exclusively in the sexual vpay because, in the normal 

 course of life at least, no other mode of reproduction is open to them ; these com- 

 prise the majority of the Conifers, especially the Firs and Araucariea;, and among the 

 flowering-plants probably also many Palms, our cereals. Flax, Hemp, Gourd, and 

 many others, and some are certainly to be found among the Cryptogams. 



The great majority of plants, however, have abundant opportunity of multiplying 

 and reproducing themselves otherwise than by means of sexual organs. Among the 

 Cryptogams indeed we may leave the spores proper out of consideration, since it is very 

 generally the case that gemmae, conidia, or other segregating portions of the shoot are 

 formed in the alternation of generations both before and after fertilisation ; and a very 

 large number of Phanerogams, especially those provided with runners, bulbs, tubers, 

 subaerial gemmae of the most Various kinds, for though they produce seeds regularly by 

 the sexual mode, almost none of these ever succeeds in germinating. It is only here 

 necessary to think of the Potato, which has for hundreds of years continually been 

 propagated by its tubers, and thus by the asexual mode. There are in fact, as 

 we shall see, a somewhat large number of cryptogamic and phanerogamic plants 

 which have in the course of time either entirely lost their sexual organs or have let 

 them become functionless, but which, nevertheless, and sometimes in perfectly astound- 

 ing numbers, multiply and propagate themselves; and on the other hand, in 

 some cases with common ubiquitous plants, the development of sexual organs de- 

 pends upon favourable conditions rarely met with, while vegetative propagation 

 occurs abundantly. In addition to less known examples the commonest of all moulds, 

 Penicillium glaucum, may be quoted as an instance ; and even in the case of the 

 largest of all the Fungi, the Hymenomycetes and Gasteromycetes it is, according to 



' The most important publications on Apogamy are : — 



Anton De Bary: ' Ober afogame Fame und die Erscheinung der Apogaitiie im AUgemcinen' 

 (Bot. Zeitg., 1878). 



De Bary: 'Beitrdge zur Morphologie und Physiologic der Pike'' (by De Bary and Woronin in 

 Abhandlungen der Senkenbergischen naturforsch. Ges. B. XII, pp. 225-370, IV. Reihe, 1881, 

 section 14, 'Entstehung und Wachsthumsursachen von Antheridien und Nebetidsten ' is particularly 

 worthy of note. 



Strasburger: • l7ier die Befruchtung itnd Zelltheilung'' (Jena, 1878, p. 63). 



