■22 



LECTURE XLI. 



the connection of these shoots with their parent shoot is sooner or later destroyed by 

 the dying off and final rotting of their older parts, so that each individual shoot can 

 now grow into a new independent plant. Many Mosses, Ferns, Equisetums, Grasses 

 and Reeds, the Strawberry, and numerous other plants may be mentioned in this 

 connection. 



It very often happens, however, that the shoots destined to become separated 

 assume special and characteristic forms, so that they may be distinguished in a 



Fig. ifify.— Tetraphis pellncidn, a Moss. A a plant bearing 

 gemma: (natural size). B the same m.agnified ; y tlie cup in 

 which the genimre collect. C longitudinal section through the 

 apex of B; d the leaves forming the cup. A' gennna? in various 

 stages of development ; the older ones are torn off from their 

 stalks by the later growth of the younger ones, and forced 

 over the edges of the cup. D a mature gemma (X 550) con- 



:ing ; 



the 



rgin of one, 



the 





veral 



layers of cells. 



Fig. 407.— Development of Telraphis from gcmm.ie. A 

 shows a gemma ifi) torn off from its stalk at a ; the protonema- 

 filainent xy has been formed by the growing out of a marginal 

 cell of the gemma, and the flat structure/ has been developed 

 as a lateral outgrowth of the protonema ; this has also put out 

 root-hairs -w -w' and -w" (X 100). Bp a flat protonema, from 

 the base of which a leaf-bud A" and root-hairs 'iuiv' have sprung. 

 The base of the flat protonema often puts forth a number of new 

 fiat protonemata before a leaf-bud is formed. 



certain sense as reproductive organs. In this connection I need only remind the 

 reader of what was said, in the lectures on Organography, concerning bulbs and tubers, 

 adding that some plants are propagated for innumerable generations solely by bulbs or 

 tubers — the potato for instance — so that reproductive organs in the narrower sense of 

 the word appear to be superfluous. In the simply organised Cryptogams (Algae and 

 Fungi) such phenomena are quite general. Deciduous cells, Conidia, are produced 

 on special supporting organs, usually in great numbers, and sometimes, as in the very 

 common mould, PenicilUu7n glaiicum, the reproduction takes place only in this way, 

 unless true reproductive organs arise under very special conditions. 



