674 Mutations 



have arisen at once, and hence the conclusion 

 that the ascidia of Nepenthes are also originally 

 due to a sudden mutation. Interrupted leaves, 

 with an ascidium on a naked prolongation of the 

 midvein, are by no means limited to the Croton 

 varieties. As stray anomalies they have often 

 been observed, and I myself had the oppor- 

 tunity of collecting them on magnolia, on clover 

 and on some other species. They are additional 

 evidence in support of the explanation given 

 above. 



In the same way double ascidia may be made 

 use of to explain the foliar cups of the teasels 

 and some other plants, as for instance, some 

 European snakeroots {Eryngium maritimum 

 and E. campestre), or the floral leaves of the 

 honeysuckle. The leaves on the stems of the 

 teasels are disposed in pairs, and the bases of 

 the two leaves of each pair are connate so as 

 to constitute large cups. We have already men- 

 tioned these cups, and recall them in the present 

 connection to use them as a prototype of the 

 double ascidia. These are constituted of two op- 

 posite leaves, accidentally connated at their base 

 or along some part of their margins. If the 

 leaves are sessile, the analogy with the teasels 

 is complete, as shown, for instance, in a case 

 of Cotyledon, a crassulaceous plant which is 



