THALLOGENS. 



Class I. THALLOGENS. 



Anaudi-ae, Link, in Berl. Mag. III. Cellulares, DC Fl. Fr.1.68. (1815). Acotyledoneie, Agardh. 

 Aph. 72. Uomoueme?e, Fries Spst. IS'25. Aphyllae, Ed. prim. Cryptophj-ta, Xin/c. //awdft. 163. 

 Thallophyta, Endl. Gen. p. 1. Amphigenae, Ad. Brong. Enumeration, p. xi. (1843/. 



The wliole of the plants stationed in this class are remarkable for the 

 extreme simi^licity of their structure. They have no wood, properly so 

 called, although in the case of some sea-weeds and Fungi they must acquire 

 considerable age. Those spirally-coated tubes which the old anatomists 

 called tracheae, because of their respiratory office, are unknown among 

 them, unless occasionally in the form of local cells connected with the 

 reproductive organs only ; and consequently upon the surface of even the 

 most perfect of them there is no sign of the organic apertures in the skin 

 called stomates or breathing-pores. They are mere masses of cells. On 

 their smface nothing is discoverable which can be regarded as analogous to 

 leaves ; for even in such sea-weeds as Hj-pnea, which resemble mosses in 

 appearance, and in some of the Lichens which seem leafy, the exact 

 symmetry which, without exception, characterises true fohage is wanting. 

 In Chara alone, w^hich is wholly leafless, do we find a sjTnmetrical arrange- 

 ment even of the divisions of the axis. Their mode of reproduction is not 

 by pollen and ovides, or by sexual apparatus, as it is usual to call those 

 parts, of which there is no sign, but by a special disintegration and soHdi- 

 fication of some part of their tissue, spontaneously effected in various ways 

 according to their kinds. It is true that such names as Antheridia and 

 Pistillidia are met with in the writings of Cr;>^togamic Botanists, from which 

 it might be inferred that something analogous at least to sexes was observable 

 among such plants ; but these are theoretical expressions, and unconnected 

 with any proof of the parts to which they are applied performing the office 

 of anthers and pistils. If it shovJd be assumed, as it has been by some, 

 that they do represent sexual organs, it is to be remembered that it is a 

 mere assumption unsupported by sufficient evidence. Even in Charas, 

 in whose globule some writers have seen a true anther, so little reason is 

 there to suppose that it deserves such a name, that, on the contrary, an 

 obseiTer, worthy of credit, assm-es us that he has seen it grow. So entirely, 

 in the simplest forms of Thallogens, is all trace of sexes missing, that in 

 some of them their rejDroductive matter has been regarded by certain writers 

 as altogether of an ambiguous nature. In their opinion, it is even uncer- 

 tain whether this matter will reproduce its like, and whether it is not a 

 mere representation of the vital principle of vegetation, capable of being 

 called into action either as a Fungus, an Alga, or a Lichen, according to 

 the particular conditions of heat, Ught, moisture, and medium, in which it 

 is placed ; producing Fungi upon dead or putrid organic beings ; Lichens 

 upon living vegetables, earth, or stones ; and Alga; where water is the 

 medium in which it is developed. Kiitzing, {A7Z9i. des Sc. n. s. vol. ii. p. 225), 

 endeavours to maintain the following propositions connected Avith this sub- 

 ject : "1st, the formation of organic matter can only take place by means 

 of the previously dissolved elements of other organic principles ; 2nd, simple 

 globules, such as Cryptococcus, Palmella, and Protococcus, can give birth 

 to different formations according to the influence of light, air, and tempera- 



