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A TEXTBOOK OF THEORETICAL BOTANY 



due to chorisis, that is to say, splitting of the petiole rudiment so that there 

 are, in effect, three petioles to each leaf, only the median one of which bears 

 a lamina. A parallel is found in some Dioscoreaceae with compound leaves, 

 in which, however, each of the petiolar members ends in a lamina. 



Fig. 1033. — Cobaea scandens. Branch 

 showing tendrils formed from dis- 

 tal leaflets of the compound leaf. 



3. Storage Leaves. — The best known examples of these organs are the 

 scales of bulbs. The latter vary greatly in the number of such scales they 

 contain, from one only, in some species of Allium, to the bulbs of Lilhim 

 auratum wdth upwards of a hundred scales. The scales likewise vary in 

 their nature. In the bulbs of Tulipa, Saxifraga gramilata, Fntillaria, Gagea 

 and Allium cepa, the common Onion, the scales are cataphylls, that is, modified 

 leaves ; but in Narcissus, Galanthus, Ornithogalum and many other genera, 



