148 Plant Classification [ch. 



Limnanthemum and Frogbit [Hydrocharis) should follow 

 one another, or that de I'Obel should have brought together 

 the Broomrape {Orobanche), the Toothwort {Lathraa), the 

 Bird's-nest Orchid {Neottia) and a number of Fungi. In 

 these latter instances the author has really arrived at 

 genuine biological (though not morphological) groups. He 

 has recognised, on the one hand, the marked uniformity of 

 the type of leaf characteristic of "swimming" water-plants, 

 and, on the other hand, he has observed the leaflessness 

 and absence of green colour, which are negative features 

 common to so many saprophytes and parasites. 



The perception of natural affinities among plants which, 

 in the sixteenth and seventeenth centuries, was gradually, 

 in a dim, instinctive fashion, arising in men's minds, is 

 perhaps best expressed in the work of Gaspard Bauhin, 

 especially in his ' Pinax theatri botanici ' (1623). This 

 work is divided into twelve books, each book being further 

 sub-divided into sections, comprehending a variable number 

 of genera. Neither the books nor the sections have, as 

 a rule, any general heading, but there are certain exceptions. 

 For instance, Book 11 is called 'de Bulbosis,' and a section 

 of Book IV, including eighteen genera, is headed ' Um- 

 belliferae.' Some of the sections represent truly natural 

 groups. Book iii. Section vi, for example, consists of ten 

 genera of Compositse, while Book iii. Section 11 includes 

 six Crucifers. Other sections contain plants of more than 

 one family, but yet show a distinct feeling for relationship. 

 For instance. Book v. Section i includes Solanum, Mandra- 

 gora, Hyoscyamus, Nicotiana, Papaver, Hypecoum and 

 Argemone — that is to say four genera from the Solanaceae 

 followed by three from the Papaveraceae. The common 

 character which brings them together here is, no doubt, 

 their narcotic property, but, although no definite line was 

 drawn between the plants belonging to these two widely 

 sundered families, the order in which they are described 

 shows that their distinctness was recognised. Some of 

 Bauhin's other groups, however, which, like that just dis- 

 cussed, are distinguished by their properties, or, in other 

 words, by their chemical features, have no pretension to 

 naturalness from a morphological standpoint. This is the 

 case with the group described in Book xi. Section iii 



