498 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



giatcB a less regularity of segmentation accompanies the greater 

 bulkiness of all the parts. Thus, as regards the embryonic 

 characters of all the parts of the sporophyte, the Ferns may be 

 ranged in a series starting with the Leptosporangiates, and 

 leading through the Schizceacea and Osmundacem to the 

 Eusporangiatcd. 



But while we thus trace the characters of the embryonic 

 tissues (in itself a somewhat technical study), it must not be 

 forgotten that these are the parent tissues of the several parts ; 

 speaking broadly, it may be stated that the several parts of 

 the mature Eusporangiate Ferns — stem, leaf, wing, root, or 

 sporangium — are of a more bulky mould than the corresponding 

 parts of the Leptosporangiates. In the case of other plants we 

 recognise a more bulky habit as commonly characteristic of 

 plants of dry situations, while a delicate habit is more usual for 

 those exposed to moist air or shaded, and there is no apparent 

 reason why we should not recognise in the series above indicated 

 a similar correlation, which would find its justification in the 

 well-known facts that such plants as Botnjchium and Ophio- 

 glossum may be found growing on exposed hillsides, and the 

 former even on dry, sandy links, while the Filmy Ferns are at 

 home in shady, damp situations, and require to be cultivated in 

 closed glass cases. 



A comparative examination of the sexual generation shows 

 that in it also a parallelism is to be traced as regards relative 

 bulk. The prothallus of the massive MarattiacecB and 

 Ophioglossacecd is itself also massive, and the antheridia and 

 archegonia are sunk in the tissue of the prothallus, thus 

 corresponding to the massive or deeply sunk sporangia of the 

 sporophyte ; in the Hymenopliyllacecd the prothallus is even 

 protonema-like and filamentous, and the sexual organs are 

 prominent and exposed, thus corresponding to the sporangia of 

 these same plants. There is, I think, every reason for 

 recognising here again that the Eusporangiate Ferns are better 

 fitted for growth under circumstances of exposure to drought 

 than the Leptosporangiate. To sum up, whether we consider 

 the embryonic condition of the stem, leaf, wing, root, or 

 sporangium, or even the prothallus and the mode of insertion of 

 its sexual organs, the Homosporous Ferns constitute a series 



