Chapter XXII. 



From Cat-tails to Eel-grasses. 

 if 



Higher seed-plants. The characters of this group are as 

 follows : the rudiments of the seeds are protected by the fusing 

 together of the specialized leaves upon which they are borne 

 into a fruit-rudiment known as the ovary. The leaves which 

 thus fuse are called carpels. In some types the ovary consists 

 of a single carpel, in others, of several carpels blended into a 

 single fruit-rudiment, while the number of carpels in a flower 

 varies in the different families. The female plant, produced in 

 the large-spore of the seed-rudiment, consists of a few cells, 

 commonly eight in number, near the time that the egg is fecun- 

 dated. The albumen of the seed is not of the nature of a 

 female plant, but is rather to be considered as the twin of the 

 embryo, and does not form until after the sperm and egg have 

 fused. In the latter characters it will be seen that the higher 

 seed-plant differs from the lower. 



The lower class of higher seed-plants. There are two prin- 

 cipal classes of higher seed-plants. The lower class is distin- 

 guished by the production of embryos with but a single seed- 

 leaf. In such plants the stem develops fibrous or woody threads 

 which become entirely mature and do not blend into a cylinder 

 from which to form a layer of growing tissue between the wood 

 and the bark. Hence the stems of perennial plants of this class 

 do not show "annual rings" of growth like those of the other 

 and higher class. For the most part the leaves have parallel 

 veins although some, such as those of the jack-in-the-pulpit, the 

 smilax and the skunk-cabbage have netted veins. The flowers 

 are ordinarily made up of five whorls of leaves, the two lower 

 and outer whorls constituting the perianth, then two whorls of 

 stamens and, in the centre, one whorl of carpels. The number 

 of leaves in a whorl is generally three, but in certain types *the 

 number varies, especially in the three inner whorls, so that 

 water-plantains, for example, produce a large number of sep- 



