60 ROTANY FOR BEGINNERS. [Oh. XL 



2G4. Involucrum. This term is derived from the Latin, in- 

 ro/ro, to wrap up; this kind of calyx is usually found at the 

 base of an umbel, as in the Carrot. It is said to be universal, 

 when it belongs equally to the whole of an aggregate flower ; 

 and partial when it encloses one floret, which, with others, con- 

 stitutes a compound or aggregate flower. The term involucrum 

 is also applied to the membranous covering in the fructification 

 of ferns. 



265. Amentj or catkin, is a kind of calyx, by some classed as 

 a mode of inflorescence ; it consists of many chaffy scales, 

 ranged along a thread-like stalk or receptacle; each scale pro- 

 tects one or more of the stamens or pistils, the Avhole forming 

 one aggregate flower. The Ament is common in forest trees ; 

 as in the Oak and Chestnut, and is also found in the Willow 

 and Poplar. In some trees the staminate flowers are enclosed 

 in an ament, and the pistillate in a perianth. 



266. Spatha signifies a sheath. It is that kind of calyx 

 which first encloses the flower, and when it expands, bursts 

 lengthwise, and often appears at some distance below it. The 

 Wild-turnip, or ARUM, furnishes an example of this kind of ca- 

 lyx, enclosing a kind of inflorescence called a spadix. From 

 the peculiar appearance of the spadix, as it stands up sur- 

 rounded by the spatha, it is sometimes called Jack in the pul- 

 pit. (See Fig. 41, a.) The spatha is common in many of our 



cultivated exotics, as in the 

 Daffodil, where it appears 

 brownish and withered af- 

 ter the full expansion of the 

 flower. You see here a re- 

 presentation, (Fig. 41, 6), 

 of the spatha of the Arum, 

 and of the Narcissus (c). 

 In the Egyptian Lily, the 

 spatha is white and perma- 

 nent, and the stamens and 

 pistils grow separately up- 

 on the spadix. Palms have a 

 spadix which is branched, 

 and often bears a great 

 quantity of fruit. 



Fig. 41. 



264, What is an involucrum? 



265. What is an ament 1 

 2G6. What is a 



