16 CURREY, ON THE SPIRAL THREADS 



pletely imperforate. Again, the question of the mode of 

 growth of the thickening layers (that is, whether they are de- 

 posited upon the outer or inner side of the primary membrane), 

 although considered by some botanists to be quite decided, 

 has lately been discussed at some length in a new work by 

 Dr. Schacht,* which shows that the subject is not yet ex- 

 hausted. The apparently fibrous structure of many liber-cells, 

 the nature of the milk-vessels, the connexion between spiral 

 and reticulated vessels, the structure of the chlorophyll gra- 

 nules and starch, are all matters upon which our present 

 knowledge must be considered imperfect. A long list might 

 be placed before the reader of questions respecting vegetable 

 structure, upon which the opinions advanced upon the one 

 side are flatly contradicted on the other. Without multiplying 

 instances, I may mention the question of the origin of the 

 embryo in phaenogamous plants as one peculiarly illustrative 

 of the point to which I have alluded upon this question. 

 This question, which although physiological in its import, can 

 only be decided by anatomical investigation, embraces two 

 parties whose views are hopelessly irreconcileable ; yet each 

 side is equally positive. Each party asserts that they have 

 actually seen that which they describe, which it is hardly 

 necessary to remark is just as impossible as that a thing 

 should be both black and white. Schleiden alleges that he 

 has set the matter at rest by his investigations, and established 

 an incontrovertible theory ; Von Mohl states that Amici has 

 destroyed Schleiden's theory at one blow, and that the matter 

 is quite settled in its principal features the other xcay. 



The spiral threads, which it is the object of this paper to 

 discuss, hold a conspicuous place amongst disputed vegetable 

 structures, so far at least as relates to the variety of the 

 opinions entertained respecting them. The genus Trichia 

 constitutes a tribe of minute fungi, growing principally, in fact 

 almost exclusively, upon rotten wood, and generally of a 

 yellowish or tawny colour. They belong to the order of the 

 Gasteromycetes, in which the spores, which are often inter- 

 mixed with hairs or threads, are developed in the interior of 

 a case, termed a peridium or sporangium. They form part of 

 the sub-tribe Myxogasteres, in which the plants first appear in 

 the form of a slimy mucilaginous stratum, out of which at a 

 later period the spore-cases are developed. The different 

 species of Trichia grow in various ways ; in T. pyriformis 

 the peridia are joined together in a fasciculate manner, in T. 

 clavata they are scattered at small distances from one another, 



* Beitrage zur Anatomie iind Physiologie der C4ewachse, by Dr. H. 

 Schacht. Bevlin, 1854. 



