THE FERN 133 



offered in park greenhouses and conservatories present excellent opportu- 

 nities to city classes for interesting studies on life liabits, especially of 

 tropical forms. 



130. Aspidium, Pteris, Adiantum, or other common fern.* * There 

 are a number of wild and greenhouse ferns, all almost equally 

 good for a type study (Ajip. 20). Examine the growing fern : 

 (1) determine the position of the stem, its habits of growth, 

 whether upright or creeping, partly above ground, or wholly sub- 

 terranean ; (2) examine the arrangement and distribution of the 

 fronds or leaves, their manner of unrolling ; (3) study fruiting 

 fronds bearing on their surface minute brown sporangia, variously 

 arranged and protected in different species of ferns. 



A. General morphology. Note : 



1. The siem, if creeping called a rooteiocA; (rhizome). Observe 

 whether it is subterranean or above ground. 



2. The roots, their distribution on the stem. 



3. The fronds, or leaves, consisting of a leafstalk (stipe) 

 and Made (lamina). Note the unrolling of the fronds. 

 Search for the scars of old fronds formerly on the 

 stem. The fronds of most ferns are compound, that is, 

 divided into segments or leaflets. Sometimes the primary 

 segments are divided again and these still again. Such 

 fronds are twice or thrice compound or branched as the 

 case may be. Describe the conditions in the frond of your 

 type. Examine the veins in the leaves and describe their 

 branching. Has the system of venation any relation to 

 the form of the margin or the compound character of 

 the frond? 



4. The sporangia on the surface of the leaves. Observe 

 their arrangement in spots or regions. Each spot is 

 called a sorus and is generally partly or wholly covered 

 by a protective membrane, the indusium. Do the posi- 

 tions of the sori bear any relation to the veins ? The 

 structure and position of the indusium is an important 

 character in the classification of ferns. 



