i6i8 



A TEXTBOOK OF THEORETICAL BOTANY 



ancient times wreaths of Laurel were used to crown victors and the statues 

 of the gods, hence the name Laurel from the Latin laus — praise. 



A number of other species possess economic and medicinal properties, 

 chiefly on account of the volatile oils which are contained in parenchymatous 

 oil glands. Among the more important of these we may mention Cinnamo- 

 mum zeylanicum and C. camphora which yield cinnamon and camphor 

 respectively. Persea gratissima is widely cultivated as a tropical fruit 

 under the name of the Alligator or Avocado Pear. It is a native of tropical 

 America Many of the trees yield valuable timber; for example the Green- 

 heart wood of Demerara is produced by Nectandra rodiaei, while Sassafras 

 officinale yields a scented wood used in the preparation of a medicinal oil. 



The Calycanthaceae are a small family with two genera, Calycanthus 

 and Chitnona7ithiis. The former includes three very widely distributed 

 species which are shrubs with opposite simple leaves and terminal acyclic 

 flowers. The perianth is composed of an indefinite number of spirally 

 arranged segments showing a gradual transition from sepals to petals. 

 There are from five to thirty stamens and an indefinite number of free 

 carpels enclosed in the hollow axis of the receptacle (Fig. 1472). Each 



Fig. 1472. — Calycdiithus floridiis. Hollow rcceptacular fruit. 



Fig. 1473. — Cliinionauthns 

 fragrans. Flowers on a 

 leafless branch in early 

 spring. 



carpel encloses two anatropous ovules. Calycanthus floridiis (Carolina 

 Allspice) is a commonly cultivated shrub. Chimonanthits fragrans (Winter 

 Sweet) is also a cultivated garden shrub whose flowers appear in early 

 spring (Fig. 1473). 



The Ceratophyllaceae have only one genus, Ceratophyllum,^W\Xh. three 

 species, of which two, C. demersum and C. submersum (Hornwort), are found 

 in Britain. They are rootless water plants with submerged leaves (Fig. 1 224), 

 which are propagated vegetatively by fragmentation following the decay of 



