206 



JOURNAL OF HORTICULTURE AND COTTAGE GARDENER. 



[ September 12, 1872. 



studies to any extent their inclinations may dictate, or their 

 leisure hours allow. 



Many assert that the veins of Ferns are a very doubtful 

 guide to generic distinction ; but it must be remembered that 

 genera at the best are but arbitrary groups formed by the 

 botanist for his own convenience, and therefore I consider any 

 variation which can be found in one group of plants, sufficient 

 to distinguish them from another group, is a great character 

 found on which to establish generic distinction ; and as the 

 venation of Ferns is very distinct and not liable to change, 

 it must, I think, be allowed that they form a safe and natural 

 guide for this purpose to the student, especially when used in 

 conjunction with the mode of growth and manner of fructifi- 

 cation. 



I shall, therefore, leave my readers to prosecute their studies 

 of the veins, and proceed to briefly examine the various modes 

 of fructification, or the manner of fruiting. 



tion of the fertile fronds, the fructification assumes a spike- 

 like character. 



In speaking of the fructification of Ferns it is usual to call 

 the place on which the sporangia are situated the receptacle ; 

 thus, when on the points of the veins it is said to be terminal, 

 a familiar example of which may be found in Leucostegia 

 j immersa (see illustration). Again, the receptacle is said to be 

 axillary when situated in the forking of the veins ; an example 

 of this form may be seen in the genus Cystopteris. The 

 basal receptacle is familiarly represented in some species of 

 Oleandra, whilst a medial receptacle may be understood by 

 the figure of Goniopteris crenata. In this case the receptacle 

 is called medial and punctiform, whilst in the ease of JPlaty- 

 cerium alcicorne it is termed amorphous, and elongated when 

 disposed in lines. The sporangia are the spore-cases which 

 contain the minute spores, and these spore-eases are borne in 

 clusters upon the receptacle. They are divided into two sec- 



Hymenodium crinitum. 



The statement may be accepted in a general way that the 

 fructification of Ferns is produced more or less regularly upon 

 the under side of the fronds, either in round masses or in 

 lines, the former being situated on the points of short veins, 

 the latter running parallel with and upon them. Some few 

 exceptions, however, must be taken to this statement, as, for 

 example, in such cases as the genus Trichomanes, where they 

 are situated upon a vein in the margin, or become exserted 

 and stand upon the very edge of the fronds. Again, in the 

 tribe Acrosticha? they cover the whole of the under side ; a good 

 idea of this may be found by the illustration of Hymenodium 

 crinitum. Another variation from this rule may be found in 

 our native Moon-wor^, Botrychium Lunaria, and the Royal 

 Fern, Osmunda regalis. In these cases, through the contrac- 



Leucostegia immersa. 



Goniopteris crenata. 



tions — those having a jointed ring surrounding them, and 

 called annulate, and those being destitute of this ring, and 

 thus exannulate. The position which this ring takes is either 

 vertical, horizontal, or oblique, each being characteristic of 

 certain genera, but I do not purpose going into details on this 

 subject. The masses of the sporangia clustered together on 

 the receptacles are called sori. These in some cases are naked, 

 in others they are covered with more or less membranous or 

 coriaceous scales, which are called indusia. This organ is 

 sometimes persistent, but more often very fugacious, and al- 

 though it affords valuable aids to generic characters, too much 

 reliance must not be placed upon it on this account. 



I shall now endeavour to give some illustrations of the 

 various kinds of indusium. The special indusia are membra- 



