REPRODUCTION, VEGETABLE (VEGETABLE OVUM). 



235 



a quantity of granular mucus. Soon this 

 last arranges itself in two masses, at opposite 



Fig. 160. 



Original parent-cell oj spores of the same, 500 dlam. 



sides of the central nucleus. Each of these 

 masses is transformed into a new nucleus, 

 from which radiating threads of mucus stretch 

 to the internal surface of the corresponding 

 half of the cell. Each new nucleus is, when 

 fully formed, vesicular, possessing a membrane 

 of extreme delicacy, and is surrounded by 

 a layer of protoplasma. At a later period 

 its contour becomes cloudy and indistinct ; 

 this change being preparatory to a second 

 division, which results in the formation of four 

 new nuclei similar to the first two ; these 



Fig. 161. 



The same, containing four vesicular nuclei, 



each cell the nucleus disappears, and is re- 

 placed by two others, between which a per- 

 pendicular septum is formed. From a repeti- 

 tion of the same process, there results a 

 cylindrical body consisting of a series of four 

 cells, the fully formed elater. 



64. No sooner are the spores of the upper 

 part of the capsule ripe, than it splits into two 

 valves ; dehiscence commences at the apex, 

 leaving, as it proceeds, the columella with the 

 loosely attached spores and elaters. 



65. Jungermannice frondosee : From Antho- 

 ceros we pass to a group of plants, which, while 

 they resemble it in their mode of growth, 

 differ from it considerably in the form of their 

 antheridia and archegonia, and still more in 

 that of the organs in which they are contained. 

 Here as in Anthoceros we follow the descrip- 

 tion of Hofmeister (Pellia epiphylla).* 



66. First period. Germination of the spores. 

 The spore is an ovoid cell, divided into four 

 by three transverse septa, and enclosed in a 

 finely granular external membrane. Of the 

 four cavities, one of the terminal ones dis- 

 tinguishes itself from the rest by the small 

 quantity of chorophylle which it contains. 

 This cavity, or rather the cell which it 

 represents, develops in germination, to the 

 first hair-like roots; while the others, by 

 successive divisions by septa in the direction 

 of the long axis of the spore, form the rudi- 

 mentary flattened stem of the young plant. 



67. The antheridia. The rudiments of the 

 antheridia make their appearance as club- 

 shaped projections of the upper surface of 

 the young spring shoots. Each such projec- 

 tion originates from a single cell of the super- 

 ficial layer by a mode of division which cor- 



*. . i . i i * l 



soon place themselves in such a manner, that 

 each would occupy one angle of a regular 



tetrahedron contained in the parent cell. Up MWTO . w . .. _ 



to this point the original central nucleus has responds in every respect with that described 

 remained; it now disappears, and six septa j n Anthoceros (659). The completely formed 

 are formed simultaneously, which radiate from 

 the centre to the circumference, one between 



every two nuclei, in such a manner as to 

 divide the parent cell into four compartments, 

 which are the special parent cells of the spores. 



Fig. 162. 



The same, divided into four compartments. 



(The above, from 155 to 162, inclusive, are after 



Hofmeister.) 



In each new cell, after this wall has become 

 thickened by the deposition of a gelatinous 

 material on its inner surface, a spore is formed, 

 which, even at the first appearance of its 

 membrane, occupies the whole cavity. As it 

 approaches maturity, it assumes a brownish 

 yellow colour, its external surface remaining 

 perfectly smooth. In those of the cells of 

 the middle layer of the half-ripe fruit, which 

 are destined to the formation of the so-called 

 elaters, the tubular form is permanent. In 



antheridium consists of a globular mass of 

 very small four-sided tessellar cells, which is 

 surrounded by an outer layer of about twenty 

 flattened cells, containing chlorophylle granules 

 in contact with each other by their margins ; 

 the whole is supported on a very short stalk, 

 consisting of only four cells. Each of the 

 small cells contains a lentil-shaped vesicle, 

 within which a spiral fibre is rolled up. This 

 fibre moves with great activity for about ten 

 minutes after its escape, revolving round its 

 own axis, and at the same time progressing 

 rapidly. The posterior extremity is slightly 

 thickened, while from the anterior which 

 tapers oft" gradually to a point, there ema- 

 nate two long and delicate cilia, like those 

 of the antherozoids of Chara. These, as well 

 as the slender prolongation of the tail, mani- 

 fest an active " winding screw-like" motion. 

 These phenomena remain in perfection only 

 for about ten minutes after the escape of the 

 filament. 



68. Archegonia. The rudiments of the ar- 

 chegonia make their appearance as oval cellular 

 bodies (from four to twelve in number) in 

 the notch, which in Pellia, as in other fron- 

 dose Hepaticae, is found in the anterior margin 



* Hofmeister, foe. cit. pp. 1020. 



