LECTURE XLL 



THE ORGANS OF REPRODUCTION. 

 GENERAL CONSIDERATIONS. ALG^; FUNGI; ARCHEGONIATA. 



It will be convenient to defer to the last of these lectures the general consider- 

 ation of the nature and physiological significance of the reproductive processes ; for to 

 a reader unacquainted with the organography of reproduction they would be at least in 

 part, if not entirely, unintelligible. The present lecture therefore will be devoted exclu- 

 sively to the description of the reproductive organs themselves. It will suffice for our 

 purpose, moreover, to select from the abundant material which laborious investigators 

 have accumulated in this province, a series of well-known and particularly striking 

 cases, from the description of which it will become sufficiently obvious that notwith- 

 standing all the variety of reproductive organs, there is nevertheless but one essential 

 point, the organographical differences being fundamentally accessory matters and 

 concerning externals only. 



All reproductive processes serve the purpose of producing new independent 

 living organisms, and this is always accomplished by a portion of the substance of 

 an already existing organism affording the material from which the new structure is to 

 proceed. 



Reproduction in this widest sense of the word may occur, especially in the 

 vegetable kingdom, in extremely various forms. In the first place there is the mere 

 regeneration by means of incidentally separated portions of a plant. It is a fact well 

 known to every one that, in the cultivation of plants, it is possible to produce new 

 plants from cut-off pieces of shoots, leaves, and often even of roots, under favourable 

 conditions of vegetation ; and it has already been explained to a certain degree in a 

 previous lecture how this occurs. Botanists have also long known that even in the 

 case of very small and in fact microscopic Algse and Fungi, accidentally isolated 

 pieces are able to acquire through growth organs which were wanting to them, and 

 to develope into new individuals. Indeed, cases are even known of small lumps of 

 protoplasm artificially expressed from the cells of Algse surrounding themselves with 

 a cellulose wall and then continuing their growth, as I have myself had the 

 opportunity of seeing in Stahl's preparations of Vaucheria. 



With such processes is connected the very common phenomenon that in 

 many plants, as a result of the normal mode of life, the individual shoots which had 

 previously been developed from common growing-points, subsequently separate from 

 one another and go on growing independently. This happens very frequently in the 

 case of species provided with stolons (runners) or rhizomes (creeping root-stocks) ; 



[3] 3A 



