196 BIOLOGICAL LECTURES. 



the vegetable kingdom, which, for this purpose, may be called 

 the Algae, Fungi, BryopJiytes, Ptet'idopliytes, and Spennato- 

 pJiytes. The representatives here chosen are not suggested with 

 any belief that they are the best possible, but with some view 

 to their availability in Eastern North America and with some 

 confidence that they are much better adapted to the purpose 

 than those used in many such courses and described in various 

 handbooks. In several published schemes the number of plant 

 types presented varies from nine to fifteen, and we may take 

 the mean as giving about the number of forms that can be 

 satisfactorily studied in the botanical half of the course. The 

 great variety of structure among the Algae and Fungi justifies 

 the selection of a third of the dozen types from each of those 

 divisions, leaving the other third to be chosen from among the 

 higher plants. 



Since the Algae include the simplest of typical plants and 

 represent the beginnings of the various lines of plant develop- 

 ment, they deserve careful study. Their chief features may 

 be illustrated by the following: — 



1. An unicellular Alga, like the Pleiirococais that often 

 forms green stains on the bark of trees, multiplying only by 

 division, or Tetmspora, found in gelatinous colonies in ditches 

 and pools in spring, or the Haeniatococcns (Sphaerella) of rain- 

 pools, with its ciliate motile stage and its brick-red resting 

 cells, may serve to emphasize the simplicity of form and struc- 

 ture of primitive organisms and to illustrate fundamental vital 

 phenomena. 



2. Spirogyra, or some similar Conjugata, presents a striking 

 case of the beginning of sexuality and of the association of 

 cells in a loose union. Theoretically, a zoosporic form, like 

 UlotJirix, would be preferable as showing an equally primitive 

 sexuality with ciliate gametes, the forerunners of the sperma- 

 tozoids of the higher plants; but the difficulty of obtaining 

 plants that show zoospores or gametes, and the far greater diffi- 

 culty of observing the union of the gametes, makes its use 

 impracticable. 



3. Fucus, the rockweed of our seashores, with its massive 

 structure and apical growth and its well-defined oogamy, pre- 



