378 



BOTANY. 



Dickson'a {rrowing in the Sandwich Islands constitute the substance- 

 known as Pulu, used somewhat in upholstery. Many ot the species, 

 are now largely grown as ornaments. 



Ferns first appeared in the Devonian, in which period no less than 

 twelve genera belonging to extinct families were represented. In the 

 Carboniferous the genera and species were exceedingly numerous, after 

 which they decreased to the present. Many Tertiary genera extend to 

 the present, and are now represented by living species. 



Order Marattiaceae, the Ringless Ferns. The protballia of the 

 ringless Ferns are thick, fleshy, and dark green in color. Tliey bear 

 antheridia in depressions upon both surfaces, and in these are pro- 

 duced spermatozoids bearing much resemblance to those of true Ferns. 

 The archegonia are also deeply sunken in the tissue of the prothallium, 

 and, according to McNab, resemble those of the Rhizocarpese. 



The asexual generation bears a close resemblance to that of true 



Pig. 368. Fig. 26?. 



Fig. 268. — A prothallinm of Boirychium Lnnaria. in longitudinal section, ac^ an 

 arcliegonium ; an, an antheridium— near to it an* others, one not yet mature, and 

 three empty ones ; w, root-hairs. X ."iO. — After Hofmeister. 



Fig. 269. — A longitudinal section of the lower part of a yonnpc plantof the same, dug 

 up 'in September, st, stem ; b, &', b'\ leaves. X 20.— After Hofmeister. 



Perns. Tlie plant-body is usually large ; its stem is generally upright. 

 Short, thick, and unbranched ; the leaves are circinately developed, as 

 in true Ferns, and are mostly very large, with pinnately or palmately 

 divided laminas ; they are provided with stipules, and in their petioles 

 is found the first collenchynia. The stem develops from a three-sided 

 apical cell, but the root is provided with a group of cells, as in the 

 Phanerogams. 



The sporangia occur on lateral veins upon the under side of the 

 leaves, and are usually confluent into one body, the sorus (often called 

 erroneously the sporangium). In Angiopteris, however, the sporangia 

 are distinct. The spnres develop from many mother-cells in each spo- 

 rangium, iustead of from one, as in true Ferns. 



The MarattiacefE are essentially tropical, extending somewhat inta 

 the warmer parts of the temperate zones. Four gt-nera are known, 

 viz. , Danaia, restricted to tropical America ; Kaulfussia and Angioptei-is, 



