CR YP TUUA J/o US T YPES. 



cJ 



CRYPTOGAMOUS TYPES. 



PTERIDOPHYTES. 

 Ferns. 



Fig. 293 is a representation of our common Polypody. You 

 may find it in almost any shatled rocky place. Running 

 horizontally beneath the surface you •will find the stem 

 of the plant, which in this case is, therefore, a rhizoinr. 

 A poi-tion of the rhizome is shown in the lower part 

 of the figure, with fibrous roots on the under side. From 

 the upi^er side are developed the leaves, which, as you see, 

 have long petioles, and if you find one which is still in the 

 bud you will observe that it is rolled up lengthwise, as 

 shown in Fig. 294. The vernation is, therefore, circi- 

 nafe, and this is the case in nearly all the Ferns. On 

 examining the back of the leaf (Fig. 293 shows the back) 

 we observe rows of brownish dots on each side of the 

 middle veins of the upper lobes. Fig. 295 is an enlarged 

 view, showing the position of these dots at the extremities 

 of the veinlets. When we put one of these dots under the 

 microscope it is seen to be a cluster of minute, stalked 

 bodies, such as that shown in Fig. 296. These bodies 

 are further found to be sacs filled with extremely fine dust, 

 and the dust consists of multitudes of rounded particles 

 all exactly' alike. They are, in sliort. spoi'e^; and the 

 sacs in which they are contained are the spore-cases, or 

 sporaiKjia : while the clusters of sporangia are ihe fruit- 

 dots, or sort. Aroimd each sporangium there is an elastic 

 jointed ring which breaks at maturity, and by its elas- 

 ticity ruptures the spore-case, which then discharges its 

 spores, as shown in the figure. The leaf of the Fern, 

 then, is something more than an ordinary foliage-leaf, 

 and is known as the frond. The i)etiole is called the 

 stipe, while the mid-rib is the rharhis. 



A spore under certain conditions develo{ies a slender thread- 

 like cell which eventually gives rise to a thin, flat, green 

 expansion, resembling that shown in Fig. 297. This is 

 called the pi'othalliiim. _ From the under surface root- 

 hairs are produced as shown in the figure. On the same 

 .surface, among the root-hairs, arise minute projections of 

 tissue in wliich are developed cells corresponding to the 

 pollen-grains of phanerogams. These projections are the 

 antheridia ; they contain cells in which are fertilizing 

 bodies known as antherozoids. Also on the under sur- 

 face of the protiiallium, near the notch, we find structures 

 analogous to the embryo-sac of the phanerogamous ovule. 

 These are the archegoniu. They are mostly flask-shape<l 



Fig. 2&4. 



Ftp. *«3. 



Fig. »7. 



