RESEARCHES ON THE CARBONIFEROUS FLORA. 265 



stems. This questionable theory no doubt produced a 

 certain prejudice in the minds of botanists against work 

 which in all other respects was excellent. 



Just before the close of his life, Williamson, with a rare 

 openness of mind, convinced himself that these views were 

 mistaken. 



The fourth group which we propose to deal with is that 

 of the Lycopodiaceous plants. It is more difficult here than 

 in previous cases to give in a few words any idea of what 

 was accomplished, for the forms investigated are numerous, 

 and a general survey of the present state of our knowledge 

 has still to be made. As is well known, Brongniart had 

 taken the same course with this group as with the 

 Calamariese. The specimens of Lepidodendron which he 

 examined [L. Harcourtii) happened to be without secondary 

 tissues, while his Sigillaria of course possessed them to a 

 conspicuous extent. Brongniart saw the distinction quite 

 clearly (for he was a good anatomist for that day as well as 

 a great systematic botanist), and attached so much im- 

 portance to it that he placed Sigillaria among Phanerogams, 

 while leaving Lepidodendron in Lycopodiacese. William- 

 son in his memoir ii. (1871), the first which treats of these 

 plants, at once attacked the position of the French palaeon- 

 tologist. He says: " I am now in a position to demonstrate 

 the complete unity of the plants which M. Brongniart has 

 separated so widely, and to show that the transition from 

 one form to another is so gradual as to necessitate the 

 inclusion of the entire series in the Lepidodendroid family". 

 Ultimately he completely justified his contention, and, with 

 perhaps one exception, brought round all his opponents to 

 his opinion. 



The earlier memoirs on Lycopodiaceae have two draw- 

 backs. First, that the author applied the terminology proper 

 to Dicotyledons not only to the sccondaiy tissues (where 

 such an application is justifiable) but also to the primary 

 structure, which in Lycopodiaceous plants is of course quite 

 peculiar. Secondly, he attached too much systematic im- 

 portance to the occurrence of secondary growth, and even 

 proposed a classification of vascular Cryptogams based on 



