170 INTRODUCTION TO CRYPTOGAMIC BOTANY. 



out any distinct conceptacle ; or finally entirely free, though 

 still collected in fasciclea, and occasionally surrounded with an 

 involucre of short branchlets. In every case the perfect spore 

 consists of a dense grumous mass surrounded by a hyaline sub- 

 gelatinous coat, consisting of at least two membranes. The 

 germination of these bodies has been well described by 

 Agardh. The situation, mode of growth, structure, &c., of 

 the conceptacles varies almost infinitely, and these modifi- 

 cations, combined with the structure of the frond, afford the 

 distinctive marks by which the genera are separated from 

 each other. Besides the conversion of the upper joints of 

 moniliform threads into so many spores, there is another 

 mode of fructification which requires notice. This cannot be 

 given, better than in the words of Dr. Harvey : " In the less 

 organised families (GongylosperTnece), the nucleus is formed 

 either from a single mother cell, from several detached mother 

 cells, or from such cells imperfectly joined together in monili- 

 form strings issuing from a central point or growing from the 

 placenta of a conceptacle. Each mother cell, which is at first 

 filled with a homogeneous endochrome, becomes by repeated 

 cell division converted into a cluster of spores at first retained 

 within its walls ; afterwards on the bursting of the wall dis- 

 persed. Thus by the evolution of one cell, a favella, or simple 

 globose nucleus, containing many spores within a hyaline 

 periderm, is formed ; by the evolution of several detached but 

 adjacent mother-cells, a compound favella or favellidium 

 results, and by the similar evolution of the cells of the moni- 

 liform series the highest form of favellidium is produced. In 

 all these cases the general nucleus, as well as the particular 

 nucleoli, is surrounded by a gelatinous or submembranaceous 

 hyaline periderm." 



145. The tetraspores, like the conceptacles, vary greatly 

 in situation ; sometimes they are lodged in particular wart- 

 like excrescences, sometimes in minute leaflets, or in linear 

 organs in which they are arranged in parallel rows, some- 

 times in the substance of the frond, at a greater or less 

 depth beneath the surface. They mostly consist of a globe 

 • See, however, Nothogenia variolosa, Mont. 



