340 BOTANY 



escape from the mother cells and are set free in the water by the separation of the 

 shields. They have the appearance of spirally-coiled corkscrew-like threads, and 

 bear two cilia at their anterior extremity (Fig. 70, A, p. 67). In the form of their 

 spermatozoids the Characeae differ from the Algae and bear a closer resemblance 

 to the Bryophyta and Pteridophyta. The female organ, or oogonium, has a brownish 

 colour, is oval in shape, and somewhat larger than the antheridia. It is attached 

 to the same cell (was) as the antheridium by means of a stalk-cell (Fig. 264, A, p). 

 Between the egg -cell and the stalk -cell are interposed a nodal cell (no) and 

 the so-called " Wendungszelle " (■»). The large egg-cell, which is full of starch and 

 oil globules, is completely enclosed by an envelope formed of five spirally-winding 

 tubes which spring from the nodal cell. The enveloping tubes terminate in a 

 crown (c) composed of five cells cut off from them by transverse walls. At the time 

 of fertilisation the enveloping tubes separate a little from each other at the ' neck 

 of the oogonium just below the crown-cell ; through the fissures thus made, the 

 spermatozoids enter the egg-cell. The egg, after fertilisation, now converted into 

 an oospore, becomes invested with a thick, colourless wall. The inner walls of the 

 tubes become thickened and encrusted with a deposit of calcium carbonate, 

 while the external walls of the tubes soon become disintegrated ; the brown inner 

 walls of the tubes, strengthened by their layer of calcium, continue as a protective 

 covering after the oospore has fallen from the parent plant. 



With few modifications, the structure of the-scxual organs is the same in the 

 other Characeae. 



The oospore, on germination, gives rise first to a simple, filamentous row of cells, 

 the proembryo. From the first node of the proembryo rhizoids are produced, 

 while at the second node there arise, together with a few simple lateral axes, one 

 or more main axes, which finally 'develop into a full-grown plant. 



The formation of tuber-like bodies (bulbils, stareh-stars) on the lower part of the 

 axes is characteristic of some species of the Characeae. These tubers, which are 

 densely filled with starch and serve as hibernating organs of vegetative reproduc- 

 tion, are either modified nodes with much shortened branch whorls (e.g. in Toly- 

 pcllopsis stelligera, when they are star-shaped), or correspondingly modified rhizoids 

 (e.g. the bulbils of Chara aspera). 



Cham crinita affords the only example of parthenogenesis (p. 68) 

 known in the vegetable kingdom ; its egg-cells, without previous fusion 

 with spermatozoids, are converted into spores capable of further de- 

 velopment. In the Flora of Northern Europe female plants only are 

 found. 



Class X 



Hyphomycetes (Fungi) 



The Hyphomycetes or Eumycetes were formerly classified collectively 

 with the Myxomycetes and Schisomycetes as Fungi. They are, however, 

 quite distinct from each of these classes, and should probably 

 be viewed phylogenetically as representing saprophytic or parasitic 

 forms of the Ghloropl^jceae, in which a complete absence of chlorophyll 

 and chromatophores has resulted from their manner of life. Their 

 cells are provided with distinct but, in most cases, very thin walls 



