REPRODUCTION, VEGETABLE (VEGETABLE OVUM). 



222 



is composed of little bunches of hyaline cells, 

 which are arranged round a central axis, 



139. 



Antheridia of Griffithsia, 30 diam. 



a, a kind of involucre is formed by a whorl of six 

 verticillate branchlats, at the points of bifurcation 

 of each of which is borne an antheridium ; 

 6, terminal tuft from surface of antheridium, 

 along with a few of the hyaline vesicles, 300 diam. 

 (Thuret). 



formed of larger cells placed end to end. At 

 the junctions of these, smaller branches are 

 given out, upon which the hyaline cells are 

 sessile. These last possess a diameter of 

 about yJ^ of an inch. 



From the above details it will be seen that 

 great difficulties lie in the way of a comparison 

 between the reproductive organs of the Flo- 

 rideaa and those of other families. Nageli 

 considers them to present a strong analogy 

 with those of the Hepaticae, with which he 

 places the Florideae in a parallel position. We 

 shall see, as we advance, how little ground 

 there is for such a view. 



The Florideae are trioecious plants : the 

 tetraspores, polyspores, and antheridia being 

 never found together in one individual. 



24. CharacecB. Although we are well ac- 

 quainted with the structure of the reproductive 

 organs of the Characese, we are, as yet, able 

 to perceive only subordinate relations between 

 them and those of other plants. These organs 

 are of two kinds ; the one being destined to 

 the production of a germ, the other to that of 

 antherozoids. The former is an oblong oval 

 body, which is placed at the junction of two 

 segments of the articulate tubular stem. It 

 consists of an oval germ-cell, invested by two 

 envelopes. The outer of these is remarkable 

 for the arrangement of the five tubular cells 

 of which it is formed, which are twisted spirally 

 round the central parts, and form by their 

 ends, at the summit, a crown of five teeth. 



The germination of Chara has been ob- 

 served and described by Vaucher.* The de- 

 velopment of the germ, which ripens in 

 autumn, does not take place until spring. It 



* Vaucher, Me'm. Soc. Hist. Nat. de Geneve, 

 torn. i. 



consists in the budding out of the central cell 

 at its apex so as to form a single tubular stalk, 

 just as in the lower Algae. 



25. The antheridium of Chara is an orange- 

 red, and globular body, which is attached to the 

 stem immediately below the germ-producing 

 organ. It consists of eight concave, rectan- 

 gular valves, joined at their edges so as to 

 form a hollow sphere. At each suture there 

 is a partition, which is directed to the centre 

 of the sphere ; while from the centre of each 

 valve there springs a cylindrical cell, the axis 

 of which is perpendicular to its inner surface, 

 so that each cell approaches the centre of the 

 sphere by its extremity. The whole anthe- 

 ridium is supported by a ninth cylindrical cell, 

 which is inserted by its base into the stem of 

 the plant, and passing up between the corners 

 of the four inferior valves, approaches the 

 other eight cylindrical cells at the centre. 

 From the extremities of the nine cells, there 

 emanate a number of flexible tubes, which are 



Fig. 140. 



a, flexible tubes from antheridium of Chara. From 

 most of the segments the antherozoids have 

 escaped ; two are in the act of escaping : b, fully 

 formed antherozoids. 400 diam. (Thuret.) 



divided by transverse partitions into a number 

 of segments. In each segment or cavity an 

 antherozoid is contained. Each antherozoid 

 is a spirally coiled fibre endowed with a power 

 of active motion, which is displayed as soon 

 as it is removed from its cell. The motion is 

 of two kinds of progression, and of revolution 

 round the axis. According to Thuret, two 

 cilia emanate from each antherozoid, a little 

 behind its anterior extremity, and it is to 

 these organs that the motion is to be attri- 

 buted.* 



26. Summary. If we take into consideration 

 only those families of the Algae in which the 

 phenomena of reproduction have been more or 

 less completely investigated, we shall find that 

 all the instances of the occurrence of bodies to 



* For further information see K. Miiller, Die 

 Entwick. der Characeen, Bot. Zeit. 1845, p. 393. 

 Kaulfuss, Die Keimung der Characeen. Leipzig, 

 1825. Varley, On the Structure of Chara in the 

 Microscropic Journal. Thuret, Ann. des Sc. Nat. 

 xvi. p. 18. 



